Effects of constant light exposure and blindness on the oxidative metabolism of selected brain areas in male rats

Male rats were housed in continuous illumination or blinded when 21 day-old and killed 69 days later. The continuous illumination exposure increased the weights of testes and sex accessory organs and reduced the pineal gland weight. Blindness decreased weights of testes, sex accessory organs and anterior pituitary. The oxygen consumption rate of the hypothalamus was higher in the blinded animals than in the controls and lower in the continuously illuminated rats. No one of such groups showed significant changes in the oxygen consumption by either the amygdala or the hippocampus.     

Midline interhemispheric fusion associated with atypical callosal dysgenesis: a mild type of holoprosencephaly

Pubertal male Wistar rats were submitted to bilateral castration and killed 7 or 14 days later; an additional group of castrated rats was submitted to ultrasound stimulation of the ventral region lying above the accessory sex glands, for 20 min a day from the 7th to the 14th day postcastration. Control intact rats were age-matched to the different treated groups. Seminal vesicle growth and secretory activity were investigated on the basis of weight and fructose content, respectively. A progressive fall in seminal vesicle weight was observed over a period of 7 (83% decrease) to 14 (92% decrease) days following castration; ultrasound treatment beginning on the 7th day prevented this additional weight reduction. Castration caused also a marked decrease (50-60%) in the fructose content of the seminal vesicle and the ultrasound energy promoted a partial recovery of the secretory activity of the gland. The results revealed a direct ultrasound stimulation of the seminal vesicle secretory activity in pubertal rats deprived of testicular androgens.     

Interactions of the bacterial pathogen Listeria monocytogenes with mammalian cells: bacterial factors, cellular ligands, and signaling

Risedronate ([1-hydroxy-2-(3-pyridinyl)-ethylidene[bis]phosphonic acid] monosodium salt) was evaluated for induction of hepatic microsomal drug metabolizing enzymes in male and female Sprague Dawley rats (N = 4/sex/dose group). Main study animals received water (vehicle control), risedronate (0.1, 0.8, 4, or 16 mg/kg/day) or phenobarbital (80 mg/kg/day, positive control) by daily oral gavage for 14 consecutive days. Recovery study animals received water, risedronate (16 mg/kg/day) or phenobarbital (80 mg/kg/day) by daily oral gavage for 14 consecutive days and then were maintained drug-free for 14 days to evaluate the reversibility of any observed effects. At the conclusion of each study the animals were sacrificed, the liver removed, weighed and the microsomal subcellular fraction prepared. The hepatic microsomal fraction was then evaluated for protein content, cytochrome P450, and the activities of aniline hydroxylase, aminopyrine N-demethylase, ethoxycoumarin O-deethylase and p-nitrophenol UDP-glucuronosyltransferase. Risedronate was well tolerated during the dosing phase of the study as evidenced by clinical observations, body weight gain and food consumption which were not significantly different from the vehicle controls. Risedronate did not significantly increase (P > 0.05) liver weight, liver/body weight ratio, protein content, P450, aniline hydroxylase, aminopyrine N-demethylase, ethoxycoumarin O-deethylase or p-nitrophenol UDP-glucuronosyltransferase in rats of either sex when compared to vehicle controls. As expected, the hepatic microsomal enzyme inducer phenobarbital significantly increased (P < 0.05) liver weight, liver/body weight ratio, protein content (males only), P450, aniline hydroxylase (males only), aminopyrine N-demethylase (males only), ethoxycoumarin O-deethylase and p-nitrophenol UDP-glucuronosyltransferase in rats relative to vehicle controls. Following the 14 day drug-free recovery period the induction parameters increased by phenobarbital reversed to vehicle control levels. The results obtained in this well controlled study indicate that risedronate is not an inducer of hepatic microsomal drug metabolizing enzymes in the rat.     

High incidence and histogenesis of seminal vesicle adenocarcinoma and lower incidence of prostate carcinomas in the Lobund-Wistar prostate cancer rat model using N-nitrosomethylurea and testosterone

The origin of chemically induced male accessory sex gland tumors was studied in Lobund-Wistar rats. Rats were treated at the age of 3 months with a single intravenous injection of 30 mg N-nitrosomethylurea (NMU)/kg body weight and given subcutaneous silastic implants filled with 40 mg testosterone propionate. Previous reports described a high incidence of prostate carcinomas in these rats with this treatment protocol. Additional animal groups included untreated controls, rats that received only an injection of 30 mg NMU/kg, and rats that were subjected to ablation of the seminal vesicle lobes prior to the treatment with NMU and testosterone. Three to 14 rats per group were sacrificed 4 to 10 months after NMU treatment and all remaining rats after 12 months. Twenty-four additional rats died or became moribund during the study. All rats were necropsied and the dorsolateral and ventral prostate and seminal vesicles with coagulating gland (anterior prostate) were examined histologically according to a standardized protocol. Lesions detected included atypical hyperplasia in all glands (resembling prostate intraepithelial neoplasia of human beings), adenomas in seminal vesicles only, and early carcinomas and adenocarcinomas in seminal vesicles and coagulating gland. Early carcinomas of the seminal vesicle, microscopically small and with invasion of the lamina propria and/or tunica muscularis, were detected as rapidly as 4 months after treatment. The vast majority (> 95%) of the grossly visible nodules/masses originated from the seminal vesicles. Testosterone treatment enhanced occurrence and increased the incidence of all lesions, particularly of seminal vesicle adenocarcinomas, from 30% (7/23) to 64% (21/33). Coagulating gland tumors were found in 21% (7/33) of the rats. Ablation of the seminal vesicle lobes reduced the incidence of seminal vesicle adenocarcinomas to 11% (3/29), and these tumors arose from tissues remaining within the parenchyma of the seminal vesicle/prostate complex after ablation. Thus, NMU-induced and testosterone-promoted male sex gland tumors of the Lobund-Wistar rat arise almost exclusively in the seminal vesicles and coagulating gland (anterior prostate), are highly invasive in seminal vesicles before attaining a grossly visible size, and progress rapidly within 4 months, spreading to adjacent tissues and other organs.     

Impairment of thymus-dependent immune functions by exposure of the developing immune system to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

The effects of TCDD exposure on the developing immune system were investigated in F344 rats. Fetal and neonatal rats were exposed to TCDD through maternal dosing (5 microgram/kg) on day 18 of gestation and on days 0, 7, and 14 of postnatal life (group I). Another group of neonatal rats was exposed to TCDD through maternal dosing on days 0, 7, and 14 of postnatal life only (group II). Body weights and thymus/body weight ratios were found to be suppressed up to 145 days of age in group I, but only up to 39 days of age in group II. Parameters of cell-mediated and humoral immune function were investigated. TCDD suppressed cell-mediated immune function without affecting humoral immune function. Suppression of T-cell function was selective in that "helper" cell function was not suppressed.     

Absorption, distribution, and excretion of [14C]patulin by rats

Adult rats of both sexes were given a single oral dose of [14C] patulin and were sacrificed at various time intervals from 4 hr to 7 days following administration of the mycotoxin. Two groups of rats were employed; the treated group had been exposed to daily oral doses of unlabeled patulin (dissolved in pH 5.0 citrate buffer) in utero and for 41-66 wk after weaning, while the controls were given the buffer only throughout gestation and for 38-81 wk after weaning. Approximately 49% of the administered 14C radioactivity was recovered from feces and 36% from urine within 7 days after dosing. Most of the excretion of labeled material occurred within the first 24 hr. All of the 14C activity detected in the urine samples was either metabolites and/or conjugates of the original [14C]patulin. About 1-2% of the total radioactivity was recovered as 14CO2 from expired air. Carbon-14 radioactivity in various tissues and organs was determined throughout the 7 day period; the most significant retention site was the red blood cells.     

The disposition of allyl isothiocyanate in the rat and mouse

The urine was the major route of excretion of radioactivity (50-80% of dose) following the oral administration (2.5 and 25 mg/kg body weight) of allyl[14C]isothiocyanate (AITC) to male and female Fischer 344 rats and B6C3F1 mice. Smaller amounts were found in the faeces (6-12%) and expired air (3-7%). The major difference between the two species was the greater retention of radioactivity after 4 days within rats (18-24% of dose) when compared with mice (2-5% of dose). Three radioactive components were found in the urine of mice and two in rats. The three components were inorganic thiocyanate, allylthiocarbamoylmercapturic acid and allylthiocarbamoylcysteine in mice, but no cysteine conjugate was found in rat urine. In the mouse, approximately 80% of the 14C was present in the urine as the thiocyanate ion whereas in the rat some 75% was as the mercapturate. This indicates that in the mouse, hydrolysis of AITC was the major metabolic pathway whereas in the rat glutathione conjugation was the major route. A species difference was seen in the amount of [14C]AITC-derived radioactivity present in the whole blood of rats and mice; measurable levels of radioactivity remained within rat blood for a longer time period (up to 240 hr) when compared with mice (96 hr). Examination of the urinary bladders of male and female rats following oral dosing with [14C]AITC showed a sex difference with greater amounts of [14C]AITC and/or its metabolites within the bladder tissue of male rats. This data is discussed in terms of the known species- and sex-specificity of the urinary bladder tumours, which occurred after long-term administration to male rats, but not to female rats or mice of either sex, in a carcinogenicity study conducted by the National Toxicology Program in the USA.     

Effect of synthetic progestins on the uptake of labelled testosterone and estradiol-17beta by the accessory genital organs of male rats

The effect of pretreatment with norethindrone (NE) or 17-hydroxyprogesterone caproate (17-OHPC) on the uptake of tritiated testosterone and estradiol-17beta by the accessory sex organs of castrated and intact rats was investigated. A selective in vivo increase in the incorporation of tritiated testosterone and estradiol-17beta was observed at 48 hours after castration. The uptake of testosterone was greatest in the epididymis, while the maximum incorporation of estradiol-17beta was by the vas deferens. Pretreatment with NE or 17-OHPC decreased the incorporation of testosterone by all the accessory organs of castrated rats. NE decreased the incorporation of tritiated estradiol-17beta in the epididymis and seminal vesicles only, while 17-OHPC decreased the uptake in all accessory organs.     

Biotransformation, excretion, and nephrotoxicity of the hexachlorobutadiene metabolite (E)-N-acetyl-S-(1,2,3,4, 4-pentachlorobutadienyl)-L-cysteine sulfoxide

The disposition of ethyl 4-(3,4-dimethoxyphenyl)-6,7-dimethoxy-2-(1,2,4- triazol-1-ylmethyl) quinoline-3-carboxylate (CAS 158146-85-1, TAK-603) after single oral dosing of 14C-labeled TAK-603 ([14C]TAK-603) at 10 mg/kg to rats and dogs was studied. In rats, the concentration of unchanged drug in plasma reached a peak (Cmax, 0.31 microgram/ml) 2 h (Tmax) after dosing of TAK-603 and declined biphasically with apparent half-lives (t 1/2 alpha, t 1/2 beta) of 1.5 and 3.6 h. In dogs, Tmax, Cmax, T 1/2 alpha, and t 1/2 beta were 1.7 h, 0.36 microgram/ml, 1.2, and 10.8 h, respectively. [14C]TAK-603 dosed orally was absorbed quantitatively in rats, while the extent of absorption in dogs was 54%. The bioavailability of TAK-603 was 53% and 42% in rats and dogs, respectively. In rats, 14C was distributed widely in various tissues, with relatively high concentrations in the liver, adrenal gland, and gut. The elimination of 14C from the thyroid was slower than that from other tissues. Unchanged TAK-603 and its pharmacologically active metabolite, M-I, which has the same potency as TAK-603, were distributed in articular soft tissues and synovial fluids, as target tissues, in rats and dogs, respectively. After oral administration of [14C]TAK-603, most of the 14C dosed was excreted within 48 h in rats and within 96 h in dogs. In both animals, a greater amount of the 14C dosed was excreted in feces than in urine. In biliary duct cannulated rats given [14C]TAK-603 intraduodenally, 69% of the dose was excreted in bile, and biliary 14C in part underwent enterohepatic circulation.     

Involvement of apoptosis in 4-vinylcyclohexene diepoxide-induced ovotoxicity in rats

Previous studies have determined that 4-vinylcyclohexene diepoxide (VCD) causes specific destruction of oocytes contained in small pre-antral (primordial and primary) ovarian follicles of Fischer 344 rats following 30 days of daily dosing with VCD. The purposes of this study were to identify the type of VCD-induced cell death occurring in small pre-antral follicles and to determine the earliest time following the onset of dosing when evidence of follicular destruction could first be detected. A significant decrease in the number of oocytes contained in small pre-antral follicles in ovaries of rats after 15 days of daily dosing (ip) with VCD (80 mg/kg) had been observed in preliminary experiments. Therefore, a study was conducted to determine the time of the onset of this follicular destruction by examination of follicular DNA integrity. Female Fischer 344 rats were dosed daily (80 mg/kg, i.p.) for 6, 8, 10, 12, or 14 days, and ovaries were removed 1, 4, or 24 hr after the final dose. Small pre-antral follicles (25-100 microns) were isolated by gentle dissociation of ovaries with collagenase, and follicles were sorted with micropipets. Genomic DNA was isolated from follicles and radiolabeled with [32P]dideoxy ATP, and the degree of fragmentation quantified by agarose gel electrophoresis and autoradiography. Degradation of DNA was evaluated by 32P content in low-molecular-weight fragments ( < 4 kilobase pairs). Degradation of DNA was not observed in follicles collected 24 hr after the final dose on any day. However, a random pattern of DNA degradation was observed, and was significantly greater (p < 0.05) compared with controls, when follicles were collected 4 hr following VCD administration on Days 10 and 12, but not on Days 6 or 8, of dosing. Although not significant, there was also evidence of DNA degradation in dosed animals on Day 14. Histological evaluation of small pre-antral follicles in ovarian sections during the early stages of VCD-induced DNA degradation (Day 10; 4 hr) demonstrated margination of chromatin along the nuclear membrane in oocytes and disruptions in focal contact between granulosa cells and oocytes, both features indicative of apoptosis. Furthermore, there was no sign of ruptured membranes in granulosa cells or oocytes or of an inflammatory response, characteristics of necrosis (pathological cell death). Whereas biochemical and morphological evidence of follicular destruction was seen 4 hr after dosing on Day 10, numbers of oocyte-containing primordial and primary follicles in VCD-treated animals were not different from controls at that time. These results demonstrate that the initial evidence of impending destruction of small pre-antral follicles is first consistently visualized following 10 days of daily dosing with VCD, although a measurable reduction in oocyte numbers has not yet occurred. Despite the fact that internucleosomal cleavage of genomic DNA was not observed, morphological evaluations support that granulosa cells and oocytes in primordial and primary follicles are destroyed via the induction of apoptosis.     

Intestinal uptake of particulate material by dexamethasone-treated rats: use of a novel technique to avoid intestinal mucosal contamination

The aim of this study was to investigate the effect of immune suppression on the uptake of particles across the wall of the intestine and the dissemination of the particles to systemic organs. Normal and dexamethasone-immunosuppressed rats were dosed orally with 0.5 mL distilled water or fluorescent polystyrene latex particle suspension containing 2.33 x 10(9) 2-microm diameter particles. One hour after particle dosing, the animals were killed by CO2 asphyxiation. The intestinal tissues and systemic organs were sampled for particle quantitation. To avoid contamination by particles adherent to intestinal mucosa the epithelium of intestinal tissue samples was removed before quantification. The number of fluorescent particles in tissues was determined by fluorescence microscopy of digests of selected samples. The uptake of particulate material across the intestinal wall was significantly (P < 0.05) increased in rats treated with dexamethasone but the number of particles transferred to systemic organs did not differ from values found for control animals. The results suggest that although dexamethasone increased intestinal permeability the apparatus or mechanisms involved in particle transport to distal sites were not affected during immune suppression.     

Influence of N-methyl-N-nitrosourea, testosterone, and N-(4-hydroxyphenyl)-all-trans-retinamide on prostate cancer induction in Wistar-Unilever rats

The influence of chemical carcinogen, hormonal stimulation, and chronic dietary administration of the synthetic retinoid, N-(4-hydroxyphenyl)-all-trans-retinamide (4-HPR), on the induction of prostate cancer in male Wistar-Unilever rats was determined. Three different tumor induction regimens were used: (a) a single i.v. dose of 50 mg of N-methyl-N-nitrosourea (MNU) per kg body weight, followed by chronic androgen stimulation via s.c. implantation of two silastic capsules containing 40 mg testosterone each; (b) a single i.v. dose of 50 mg of MNU per kg body weight (no testosterone treatment); and (c) chronic androgen stimulation with implanted testosterone capsules (no MNU treatment). In a fourth series of animals, the incidence of spontaneous prostate tumors was determined in groups of rats receiving neither carcinogen nor hormone stimulation. Within each series, parallel groups of animals were fed a control (vehicle-supplemented) diet or control diet supplemented with 4-HPR beginning 1 day after carcinogen administration; retinoid administration was continuous until termination of the study at 450 days. The incidence of accessory sex gland cancer in rats treated sequentially with MNU + testosterone was >60%, in comparison with cancer incidences of <20% in rats receiving MNU only and <5% in rats treated with testosterone only. No spontaneous accessory sex gland tumors were observed in rats receiving no carcinogen and no testosterone. Tumor induction in the accessory sex glands by MNU + testosterone was relatively specific for the prostate: the incidence of carcinoma of the dorsolateral/anterior prostate was more than 5-fold greater than the incidence of cancer present only in the seminal vesicle. 4-HPR conferred no protection against cancer induction in the prostate by any regimen of MNU and/or testosterone. These results demonstrate the importance of both carcinogen exposure and hormone stimulation on the induction of neoplasia in the prostate of Wistar-Unilever rats.     

Chemoprevention of rat prostate carcinogenesis by 9-cis-retinoic acid

A chemoprevention study was conducted to evaluate the activity of 9-cis-retinoic acid (9-cis-RA) as an inhibitor of prostate carcinogenesis in male Wistar-Unilever (HsdCpb:Wu) rats. After pretreatment with a sequential regimen of cyproterone acetate (50 mg/kg/day for 21 days) and testosterone propionate (100 mg/kg/day for 3 days), groups of 40 rats received a single i.v. injection of N-methyl-N-nitrosourea (MNU; 30 mg/kg body weight). Beginning 2 weeks after carcinogen administration, rats received chronic exposure to testosterone administered in s.c. implanted silastic capsules. The study was terminated at 13 months after MNU administration, and prostate cancer incidence was determined by histopathological evaluation of step sections of accessory sex glands. Continuous dietary administration of 9-cis-RA at 100 mg/kg diet or 50 mg/kg diet beginning 1 week before MNU administration reduced cancer incidence in the dorsolateral + anterior prostate from 65% in dietary controls to 18 and 20%, respectively (P < 0.001 for both comparisons). Similarly, these dose levels of 9-cis-RA reduced the incidence of cancer in all accessory sex glands from 79% in dietary controls to 48 and 33% (P < 0.01 for both comparisons), respectively. Chronic dietary administration of 9-cis-RA induced no gross or organ-specific toxicity in any animal and did not suppress group mean body weight gain. The potent anticarcinogenic activity of 9-cis-RA in the rat prostate, when considered with its apparent lack of toxicity in rodents, suggests that this and other ligands for the retinoid X receptor merit consideration for evaluation in clinical prostate cancer chemoprevention trials.     

Toxicity evaluation of petroleum blending streams: inhalation subchronic toxicity/neurotoxicity study of a light alkylate naphtha distillate in rats

A 13-wk inhalation study was conducted with Sprague-Dawley CD rats (12/sex/group) were exposed by inhalation for 13 weeks to a light alkylate naphtha distillate (LAND-2, C4-C10; average molecular weight 89.2) at actual average concentrations of 0 (room air), 668, 2220, or 6646 ppm, 6 h/d, 5 d/wk; 12 additional rats/sex in the control and high dose groups were held after final exposure for a 4-wk recovery period. The highest exposure concentration was 75% of the lower explosive limit. Standard parameters of subchronic toxicity were measured throughout the study; at necropsy, organs were weighed and tissues processed for microscopic evaluation. Neurotoxicity evaluations consisted of motor activity (MA) and a functional operational battery (FOB) measured pretest, during 5, 9, and 14 wk of the study, and after the 4-wk recovery period. Whole-body perfusion and microscopic examination of selected organs and nervous tissue from the control and high dose rats were conducted at the end of exposure. No test-related mortality or effects on physical signs, body weight, or food consumption were observed. Statistically significant increases in absolute and relative kidney weights in high-exposure males correlated with microscopically observed hyaline droplet formation and renal nephropathy, effects in male rats that are not toxicologically significant for humans. Increased liver weights in both sexes at the highest dose had no microscopic correlate and appeared reversible after the 4-wk recovery period. Exposure to LAND-2 at any dose did not produce neurotoxicity measured by MA, FOB, or neuropathology. The no-observed-effects level (NOEL) for LAND-2 was 2220 ppm for subchronic toxicity and > or =26646 ppm for neurotoxicity.     

A randomized study comparing retroperitoneal drainage with no drainage after lymphadenectomy in gynecologic malignancies

Drug-nutrient interactions affecting chromium were investigated in this study. Rats were injected with indomethacin to reduce endogenous prostaglandin synthesis and dosed with prostaglandin analogues or prostacyclin. Effects on absorption, tissue distribution and urinary excretion of 51Cr from 51CrCl3 were evaluated using a 2 x 4 factorial experimental design. Forty-eight adult male rats were food deprived for 12 h and then injected intraperitoneally with indomethacin (5 mg/kg body wt) or placebo. Thirty minutes later, rats were intubated and dosed with one of four treatments: a prostaglandin E1 analogue (misoprostol) at 50 microg/kg body wt; a prostaglandin E2 analogue (16,16-dimethylprostaglandin E2) at 7.5 microg/kg body wt; prostacyclin at 20 microg/kg body wt; or control (7.64 mmol/L Tween-80 suspended in 0.15 mol/L NaCl containing 0.48 mol/L ethanol). Immediately after intubation, rats were dosed with 3.7 mBq of 51CrCl3 by micropipette. Blood was collected from the tail at intervals after 51Cr dosing. Six hours after dosing, 51Cr rats were exsanguinated by cardiac puncture. Indomethacin, an inhibitor of prostaglandin synthesis, significantly increased (P < 0.05) 51Cr in blood at all time periods tested except at 15 min. In tissues, indomethacin significantly increased 51Cr retention. Urinary 51Cr excretion at 6 h was higher (P < 0.05) in indomethacin-pretreated rats than in control rats. Administration of indomethacin, which blocks prostaglandin synthesis, enhanced 51Cr absorption, whereas dosing with 16,16-dimethylprostaglandin E2 decreased 51Cr absorption.     

Dosing-induced stress causes hepatocyte apoptosis in rats primed by the rodent nongenotoxic hepatocarcinogen cyproterone acetate

It has been proposed that several nongenotoxic compounds act as hepatocarcinogens by suppressing the apoptosis that would normally act to remove damaged or potentially initiated cells from the liver. During our investigations of this hypothesis using a widely applied protocol, we have found that the stress induced by the process of gavage dosing can induce massive apoptosis in livers uniquely primed by withdrawal of the hepatomitogen cyproterone acetate from the hyperplastic rat liver. This effect of gavage dosing was not seen in livers of naive animals. Apoptosis was measured by both in situ end labeling (ISEL) of the DNA damage associated with programmed cell death and conventional hematoxylin and eosin (H&E) staining of apoptotic morphology. Apoptotic rates measured by H&E increased significantly from 0.005 +/- 0.010% on Day 11 to 0.657 +/- 0.315% of hepatocytes on Day 15, 4 days after cessation of 10 days dosing with CPA (120 mg/kg). The readministration of CPA suppressed > 89% of this Day 15 apoptosis. However, the readministration of vehicle alone (corn oil) caused a 390% increase in apoptosis to 2.56 +/- 1.31% of hepatocytes. Similar results were obtained using ISEL. Measurements of liver to body weight ratios and total DNA per liver reflected these changes in cell loss by apoptosis. In a second experiment, CPA was administered for 10 days as before then animals were subjected to readministration of CPA in corn oil, CPA in saline, corn oil, saline, or sham dosed. Again, apoptosis was dramatically suppressed by the readministration of CPA in either vehicle but was dramatically increased to around 2% of hepatocytes in all other groups, including the sham dosed group. Data on food consumption provided no evidence for a reduction in food intake as a causative agent but rather pointed to a less efficient usage of food in the stressed animals. The ability of stress to induce liver apoptosis should be borne in mind in the design and interpretation of future toxicological studies aimed at understanding the putative suppression of apoptosis by liver nongenotoxic carcinogens and other toxicants.     

The effects of pineal indoles given late in the light period on reproductive organs and pituitary prolactin levels in male golden hamsters

Intact and pinealectomized adult male hamsters kept in light:dark cycles of 14:10 (in hours) were given daily injections of either 25 microgram melatonin, 5-methoxytryptophol, N-acetylserotonin, or 6-hydroxymelatonin at 19.00 hours (13h after lights on). The injections were continued for 50 consecutive days. The daily melatonin injections significantly elevated body weights and depressed the growth of the testes and accessory sex organs and pituitary prolactin levels in intact hamsters. By comparison, in pinealectomized animals daily afternoon melatonin injections failed to alter body or testicular weights or pituitary prolactin levels. These findings indicate that for single injections of melatonin to be antigonadotrophic in the male hamster, the pineal must be intact. In intact animals, 5-methoxytryptophol and N-acetylserotonin slightly depressed the growth of the reproductive organs and pituitary prolactin levels, respectively. Again, these effects were negated by removal of the pineal gland. 6-Hydroxymelatonin was without influence on any of the parameters of reproduction that were measured.     

Blood lipids during normal and early weaning in rats

In young rats reared with their mothers, a gradual increase of serum cholesterol, triglycerides, phospholipids and total lipids was found between the 7th and the 18th to 22nd postnatal day. Then the concentrations of lipids gradually decrease. Early weaning at the 18th postnatal day causes a precocious decrease of the concentration of all studied lipids in blood so that their values on days 22 and 26 are significantly lower than in animals weaned on the 30th postnatal day. The body weight of early weaned rats decreases only slightly and returns to normal by the 30th day. The changes in serum lipids after early weaning are caused by differences in the amount of cholesterol and other lipids in breast milk, in comparison with those in the standard laboratory diet. Perhaps they may participate in disturbing the homeostatic equilibrium of cholesterol in early weaned rats.     

90-day feeding and one-generation reproduction study in Crl:CD BR rats with 17 beta-estradiol

Over the past several years, there has been increasing concern that chemicals and pesticides found in the environment may mimic endogenous estrogens, potentially producing adverse effects in wildlife and human populations. Because estrogenicity is one of the primary concerns, a 90-day/one-generation reproduction study with 17 beta-estradiol was designed to set dose levels for future multigenerational reproduction and combined chronic toxicity/oncogenicity studies. The purpose of these studies is to evaluate the significance of a range of responses as well as to provide benchmark data for a risk assessment for chemicals with estrogen-like activities. This 90-day/one-generation reproduction study was conducted in male and female Crl:CD BR rats using dietary concentrations of 0, 0.05, 2.5, 10, and 50 ppm 17 beta-estradiol. Endpoints were chosen in order to evaluate both subchronic and reproductive toxicity. In addition, several mechanistic/biochemical endpoints were evaluated for their usefulness in follow-up studies. In the P1 generation, dietary administration of 2.5, 10, and 50 ppm 17 beta-estradiol produced dose-dependent decreases in body weight, body weight gain, food consumption, and food efficiency. At 10 and 50 ppm 17 beta-estradiol, minimal to mild nonregenerative anemia, lymphopenia, decreased serum cholesterol (50 ppm only), and altered splenic lymphocyte subtypes were also observed in the P1 generation. Additionally, at these concentrations, there were changes in the weights of several organs. Evidence of ovarian malfunction, characterized by reduced numbers of corpora lutea and large antral follicles, was observed at 2.5 ppm 17 beta-estradiol and above. Other pathologic changes in males and females fed 10 and 50 ppm 17 beta-estradiol included centrilobular hepatocellular hypertrophy; diffuse hyperplasia of the pituitary gland; feminization of the male mammary glands; mammary gland hyperplasia in females; increased number of cystic follicles in the ovary; hypertrophy of the endometrium and endometrial glands in the uterus; degeneration of seminiferous epithelium; and atrophy of the testes and the accessory sex glands. In the reproduction portion of this study, rats fed 10 or 50 ppm 17 beta-estradiol did not produce litters. While there was no evidence that the 50 ppm treated rats mated, 33.3% of the rats fed 10 ppm mated but did not produce litters. No effects on mating and fertility indices were observed in rats fed 0.05 and 2.5 ppm 17 beta-estradiol. Pup weights at birth were statistically decreased relative to control in the groups fed 0.05 and 2.5 ppm 17 beta-estradiol. Weights of the rats in the 0.05 ppm group recovered by postnatal day 4 and remained similar to control throughout the remainder of the study. The mean gestation length of the 0.05 ppm group was slightly, albeit not statistically significantly, shorter (0.5 days) than that of the control group, which may have contributed to the decrease in birth weight of the 0.05 ppm group. In contrast, the weights of the F1 generation rats fed 2.5 ppm 17 beta-estradiol remained decreased relative to the control group throughout the study. Parental administration of 17 beta-estradiol did not alter anogenital distance in male or female pups. The onset of sexual maturation, as measured by day of preputial separation in males and day of vaginal opening in females, was delayed in male rats fed 2.5 ppm (by 8.2 days) and was hastened in female rats fed 0.05 and 2.5 ppm (by 1.6 and 8.8 days, respectively). The age at vaginal opening ranged from 26 to 37, 26 to 35, and 21 to 25 days for rats fed 0, 0.05, and 2.5 ppm 17 beta-estradiol, respectively. Hence, the range of age at vaginal opening was similar between the control and 0.05 ppm group. The organ weight and pathologic alterations observed in the adult F1 generation rats were similar to those observed in the P1 generation rats. (ABSTRACT TRUNCATED)     

Metabolism and biochemical effects of 3,3',4,4'-tetrachlorobiphenyl in pregnant and fetal rats

The metabolism and distribution of a single oral dose of 25 mumol 14C-labelled 3,3',4,4'-tetrachlorobiphenyl (14C-TCB) were investigated in pregnant female Wistar rats and their fetuses. TCB was administered on day 13 of gestation and the elimination was followed for 7 days. Non-pregnant rats were treated similarly for comparison. Fecal elimination of 14C-TCB derived radioactivity was significantly lower in pregnant rats than in non-pregnant rats. The major metabolite found in adult liver and plasma, placental tissue, whole fetuses and fetal plasma was 3,3',4',5-tetrachloro-4-biphenylol (4-OH-TCB). Tissue levels (liver, abdominal fat, skin, skeletal muscle, kidney and plasma) of 14C-TCB-derived radioactivity declined by 65-85% over a 7-day period following administration in the adult animals. However, 14C-TCB-derived radioactivity accumulated more than 100-fold in the fetuses over the same time period, and GC/MS analysis revealed that the fetal accumulation in radioactivity was due primarily to 4-OH-TCB, and not the parent compound. On day 20 of gestation, concentrations of 4-OH-TCB were 14 times greater in fetal plasma than maternal plasma. Treatment with 14C-TCB significantly reduced plasma thyroxine levels by at least 28% up to 7 days after administration in non-pregnant animals and up to 4 days after administration in pregnant rats (31% decrease). By 7 days after administration plasma thyroxine levels had returned to control levels in the TCB-treated pregnant rats. However, fetal plasma thyroxine levels were significantly decreased by 35% in fetuses from 14C-TCB-treated dams 7 days after TCB administration. Hepatic microsomal ethoxyresorufin-O-deethylase (EROD) activity was significantly induced in TCB-treated dams relative to controls at 4 and 7 days after administration, while no EROD activity was detected in hepatic microsomes from control or TCB treated fetal rats at day 20 of gestation. These data suggest that hydroxylated metabolites of polychlorinated biphenyls may play a role in the development toxicity of these compounds.