PNU 157706, a novel dual type I and II 5alpha-reductase inhibitor

PNU 157706 is a novel dual inhibitor of 5alpha-reductase (5alpha-R), the enzyme responsible for the conversion of testosterone (T) to 5alpha-dihydrotestosterone (DHT). Tested on a crude preparation of human or rat prostatic 5alpha-R, PNU 157706 caused enzyme inhibition with IC50 values of 20 and 34 nM, respectively, compared to the values of 32 and 58 nM shown by finasteride. Furthermore, PNU 157706 was highly potent in inhibiting human recombinant 5alpha-R type I and II isozymes, showing IC50 values of 3.9 and 1.8 nM and, therefore, it was several folds more potent than finasteride (IC50 values of 313 and 11.3 nM), particularly on the type I isozyme. PNU 157706 was shown to have no binding affinity for the rat prostate androgen receptor (RBA 0.009% that of DHT). In adult male rats, a single oral dose of 10 mg/kg of PNU 157706 caused a marked and longer lasting reduction of prostatic DHT than did finasteride (at 24 h inhibition by 89 and 47%, respectively). In prepubertal, T- or DHT-implanted castrated rats, PNU 157706, given orally for 7 days at the dose of 10 mg/kg/day, markedly reduced ventral prostate weight in T- but not in DHT-implanted animals, thus showing to be devoid of any anti-androgen activity. In adult rats treated orally for 28 days, PNU 157706 resulted markedly more potent (16-fold) than finasteride in reducing prostate weight, the ED50 values being 0.12 and 1.9 mg/kg/day, respectively. These results indicate that PNU 157706 is a promising, potent inhibitor of both type II and I human 5alpha-R with a very marked antiprostatic effect in the rat.     

The regulation of gonadotropin-releasing hormone-induced calcium signals in male rat gonadotrophs by testosterone is mediated by dihydrotestosterone

The biological effects of testosterone (T) may be mediated directly by T or indirectly by its metabolites, dihydrotestosterone (DHT) and estradiol. The present study examined whether the metabolism of T is involved in the regulation of GnRH-induced Ca2+ signaling at the pituitary. In gonadotrophs from castrated rats, a significantly greater percentage of gonadotrophs demonstrated oscillatory Ca2+ responses to 100 nM GnRH than cells from intact rats (72% vs. 24%; P < 0.05). This increase was prevented by the administration of T propionate (0.1 mg/kg x day), DHT benzoate (2 mg/kg x day,), estradiol benzoate (EB; 5 microg/kg x day), or the combination of the above doses of DHT benzoate and EB. In all cases the proportion of gonadotrophs from the steroid-treated rats having oscillatory Ca2+ responses to 100 nM GnRH was between 21-25% (P > 0.05, compared with intact rats). To assess the importance of T metabolism, intact male rats were treated with the aromatase inhibitor letrozole (1 mg/kg x day), the 5alpha-reductase inhibitor finasteride (50 mg/kg x day), or their respective vehicles for 7 days. Letrozole had no effect on GnRH-induced Ca2+ signals, serum LH concentrations, or ventral prostate or testes weight. Finasteride treatment, however, mimicked the effects of castration, with significantly more gonadotrophs exhibiting Ca2+ oscillations in response to 100 nM GnRH than gonadotrophs from the vehicle-treated group (71% vs. 20% respectively; P < 0.05). Finasteride also caused a significant (P < 0.05) decrease in prostatic weight and DHT concentration, but had no significant effect on either prostatic T or serum LH concentrations. These findings suggest that in the intact male rat, the effects of T on GnRH-induced Ca2+ signaling are preferentially mediated via DHT. The results of this study also show that in the absence of androgens, estradiol may regulate GnRH-induced Ca2+ signaling in the male rat pituitary.     

Prognostic significance of tumour markers in endometrial cancer

BACKGROUND: Steroid 5 alpha-reductase is implicated in the pathogenesis of benign prostatic hyperplasia (BPH). We studied the in vitro and in vivo effects of FR146687, a new inhibitor of 5 alpha-reductase. METHODS: Two isozymes of rat and human 5 alpha-reductases were expressed in 293 cells. In vivo effects of drugs were evaluated on rat and dog prostates. Castrated immature rats were injected with testosterone propionate (TP) or 5 alpha-dihydrotestosterone propionate (DHTP) to induce growth of the ventral prostates. Testosterone and 5 alpha-dihydrotestosterone (DHT) contents in rat and dog prostates were measured by gas chromatography-mass spectrophotometry (GC-MS). RESULTS: FR146687 showed noncompetitive inhibition in both isozymes and no inhibitory effects on other steroid oxidoreductases. In mature rats and castrated immature rats treated with TP, FR146687 dose-dependently reduced ventral prostate and seminal vesicle weight at doses above 0.1 mg/kg, while castrated immature rats treated with DHTP were not affected by FR146687. FR146687 showed more potent reduction of rat prostates than finasteride. DHT concentration in the prostates was significantly reduced when FR146687 was administered to rats and beagles. CONCLUSIONS: FR146687 is a dual inhibitor for 5 alpha-reductase isozymes and significantly reduced the growth and DHT content in the prostate.     

Urogenital anomalies in fetal rats produced by the anticancer agent 4(5)-(3,3-dimethyl-1-triazeno) imidazole-4-carboxamide

Pregnant Wistar rats injected intraperitoneally on gestational day 12 with single doses (100-1,000 mg/kg) or 600 mg/kg of 4(5)-(3,3-dimethyl-1-triazeno) imidazole-4-carboxamide (dic) were autopsied on day 21 (100-1,000 mg/kg) or at 24-hour intervals on days 13-20 (600 mg/kg). Controls received CMC on the same schedule. All fetuses were weighed and examined for urogenital system (UGS) malformations. Those given 600 mg/kg were also studied histologically. DIC produced significant growth retardation at all doses on day 21 (18-72%). UGS malformations occurred in 27-67% of the fetuses at 200-400 mg/kg and in 100% of those given 600 mg/kg or more of DIC. Abnormalities included renal growth inhibition, fusion, ectopia, and ureteropelvic dilatation. At 600 mg/kg renal and body weights were reduced 40 and 55%, respectively. Ureteropelvic dilation was common, and cortical glomeruli, nephric collecting tubules, and papillae were retarded in development. The juxtamedullary glomeruli were well developed. Proximal nephric tubular mitotic activity was 85% greater than in control animals (day 17). On the basis of pertinent morphological and physiological data, it is postulated that the dilated upper urinary tracts represent functional hydronephrosis incident to severe renal retardation and its resultant compensatory response.     

Cryosurgical ablation of the normal ventral prostate plus adjuvant does not protect Copenhagen rats from Dunning prostatic adenocarcinoma challenge

PURPOSE: We wished to determine if cryosurgical ablation of the normal ventral prostate of Copenhagen rats confers protective immunity against a subsequent challenge with Dunning R3327 MatLyLu prostatic adenocarcinoma. In human melanoma, tumor antigens have been characterized as normal cellular proteins. We reasoned that cryosurgical ablation of the normal prostate along with immunostimulatory adjuvants might release prostatic antigens to the immune system engendering an immune response and rendering rats immune to prostatic cancer cells. MATERIALS AND METHODS: On day 0, Copenhagen rats underwent cryosurgical ablation of the normal ventral prostate, cryosurgery and intraprostatic injection of Complete Freund's Adjuvant (CFA), CFA injection alone, or laparotomy alone. On day 21, animals received a subcutaneous challenge of MatLyLu tumor cells. Tumor dimensions were recorded at regular intervals by a single blinded investigator. RESULTS: Animals receiving cryosurgical ablation of the normal ventral prostate or intraprostatic CFA developed tumors more frequently than animals receiving laparotomy alone and the effect was statistically significant if animals received both cryosurgical ablation of the prostate and intraprostatic CFA (3 experiments, 1 x 10(4) MatLyLu cells), total number with tumors/total number challenged: laparotomy alone 3/17, cryosurgical ablation 7/17, cryosurgery plus CFA 10/16 (p = 0.013 versus laparotomy, Fisher's exact test), CFA alone 9/17. CONCLUSIONS: Cryosurgical ablation of the normal rat ventral prostate and intraprostatic CFA does not protect against and can enhance the tumorigenicity of MatLyLu prostatic cancer cells at distant sites. This could be occurring through specific immunologic effects or non-specific mechanisms induced by cryosurgery and CFA.     

The role of dopaminergic and serotonergic mechanisms in the development of swimming ability of young rats

Neonatal swimming behavior was studied after a single subcutaneous injection of L-dopa methyl ester (50 mg/kg; 200 mg/kg) apomorphine (0.1 mg/kg; 1.0 mg/kg), DL-amphetamine (0.5 mg/kg; 10 mg/kg), haloperidol (0.5 mg/kg; 1.0 mg/kg), L-tryptophan (50 mg/kg; 100 mg/kg), methysergide (1.0 mg/kg; 5.0 mg/kg) as well as intraventricular injection of 100 microgram 6-OHDA. 1-, 3-, 5- and 7-day-old rats were placed into a temperature-controlled aquarium (37 degrees C) and the pattern of motor coordination, latency time to swimming (LTS) and the number of foreleg strokes for 10 s (FS) were measured. When compared to the physiological saline-injected controls, rats that received L-dopa showed a striking increase of FS at all ages but the most striking improvement of motor coordination was found in newborn rats. On day 1 both doses of DL-amphetamine induced increases in FS and improvement of motor coordination, whereas apomorphine failed to show any effect at this age. On days 3, 5 and 7 low doses of DL-amphetamine and apomorphine increased the FS. However, high doses resulted in a decrement in swimming performance. Haloperidol impaired swimming on day 1 but produced a significant increase of FS on days 5 and 7. Neonatal injection of 6-OHDA delayed development of motor coordination, reduced FS and increased LTS. On days 3, 5 and 7 high doses of L-tryptophan elicited an increase of FS, while high doses of methysergide caused significant impairment of performance. It is suggested that the brain rapidly converts the administered L-dopa to dopamine during the first week of life and there appears to be a strong dependent relationship between the pattern of motor coordination and the amount of available dopamine in the developing brain.     

Effects of hypophysectomy and prolactin replacement therapy on prostatic response to androgen in orchiectomized rats

The effects of hypophysectomy and prolactin replacement therapy on prostatic response to androgen in orchiectomized rats were studied. Castration 23 days prior to treatment with testosterone propionate (TP), followed by hypophysectomy 13 days before TP treatment, and then treatment with 1 mg TP every other day for 16 days caused a greater decrease in body weight, prostatic weight, and the level of citric acid in the prostate than did TP treatment, castration, and sham hypophysectomy. This suggests the existence of a pituitary factor in the maintenance of prostatic integrity. Prolactin replacement therapy in hypophysectomized, castrated,TP-treated rats significantly (p less than .005) increased the prostatic weight and both the content and concentration of citric acid. The results confirm previously reported observations that the prostatic response to androgens is markedly reduced by hypophysectomy in castrated rats, and that prolactin acts synergistically wtih testosterone in promoting prostatic growth and the concentration of citric acid in the prostate. The direct effects of both hypophysectomy and prolactin replacement therapy on the ventral and dorsolateral lobes of the prostate were also demonstrated.     

Blockade of androstenedione-induced stimulation of androgen-sensitive parameters in the rat prostate by combination of Flutamide and 4-MA

In order to mimic the human situation in which adrenal steroid precursors are converted to the active androgen dihydrotestosterone (DHT) in prostatic tissue, we have used castrated rats supplemented with the precursor steroid androstenedione (delta 4-dione) released from Silastic implants. While it is well known that the action of DHT can be partially neutralized by antiandrogens which compete for binding to the androgen receptor, we have used 17 beta-N,N-diethylcarbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one (4-MA), an inhibitor of 5 alpha-reductase, the enzyme which converts testosterone into DHT, in order to decrease intraprostatic DHT levels and thus facilitate the action of the antiandrogen. Animals were treated for 7 days with Flutamide (FLU, 2 mg) or 4-MA (4 mg) injected subcutaneously, twice daily, alone or in combination. 4-MA administered alone caused a 54% inhibition of delta 4-dione-stimulated ventral prostate weight while FLU exerted a 74% inhibitory effect and 4-MA+FLU further improved inhibition to 81%. We then measured, by in situ hybridization, the levels of prostatic mRNAs encoding the C1 and C3 components of the prostatic binding protein (PBP) which are highly specific and sensitive markers of androgen action. PBP-C3 mRNA levels fell by 95% following castration while treatment with delta 4-dione completely reversed the effect of castration. Administration of FLU or 4-MA independently caused 33% and 10% decreases, respectively, of PBP-C3 mRNA levels stimulated by delta 4-dione while the combination of both compounds further inhibited PBP-C3 mRNA levels to reach a 55% inhibition. Similar effects were observed on PBP-C1 mRNA levels.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Argon laser punctal therapy versus thermal cautery for the treatment of aqueous deficiency dry eye syndrome

1. Pregnant Wistar rats were treated orally with a single dose of 100 microg 3,3',4,4'-tetrachlorobiphenyl (PCB 77)/kg b.w. or 10 microg 3,3',4,4',5 pentachlorobiphenyl (PCB 126)/kg b.w. on day 15 of pregnancy. The control rats received peanut oil at the same day. Developmental landmarks were assessed in all offspring rats and reproductive effects of PCB 77 and PCB 126 on male offspring were studied on postnatal day 65 (at puberty) and on postnatal day 140 (at adulthood). 2. The ano-genital distance as well as the ratio ano-genital distance to body length was reduced in male pups of the PCB 126 group and the age at vaginal opening was significantly delayed in the female pups. 3. Testis, brain weights and daily sperm production were permanently increased and seminal vesicle weights were decreased in male offspring of the PCB 77 group. In male rats of PCB 126 group, the brain weights were permanently increased and ventral prostate weights permanently reduced. In both PCB groups, however, serum testosterone concentration was reduced only at adulthood. Additionally, the male rats of the PCB 126 group showed alterations in sexual behavior. In these rats the number of mounts with intromissions was significantly increased. 4. The results of this study show that PCB 126 elicits some TCDD-like reproductive effects after in utero exposure, while the reproductive effects of in utero exposure to PCB 77 on male offspring may be attributed to the neonatal hypothyroidism induced by the substance during early fetal development. Further studies using multiple doses and providing thyroid hormone data will be necessary to support this hypothesis.     

Clinical study on chlormadinone acetate alone followed by combination with LH-RH analogue for prostatic cancer: effects on lipid metabolism

Twenty-four previously untreated patients with a diagnosis of prostatic cancer were treated with chlormadinone acetate (CMA) alone (100 mg/day) for 4 weeks, and luteinizing hormone-releasing hormone analogue (LH-RHa) was added for the next 24 weeks. Marked decreases in blood LH, testosterone (T), prostate specific antigen (PSA), gamma-seminoprotein (gamma-Sm), and prostatic acid phosphatase (PAP) were observed after a single dose of CMA. T levels were significantly increased 3 days after the initial dose of LH-RHa, and did not return to the pretreatment level. There were no significant increases in any of the markers, nor were there any flare-up cases. Triglyceride levels, which were slightly elevated before the start of treatment, were significantly decreased 24 weeks after the completion of combined therapy. PSA was evaluated as partial response (PR) or better in 86.7% of the patients. Overall evaluation showed PR or better in 75.0% of the patients. These findings suggest that prior administration of CMA followed by combined administration with LH-RHa is useful in the treatment of prostatic cancer. No negative effects on lipid metabolism were observed at any time during the treatment period.     

Protective effect of liposome encapsulation on paclitaxel developmental toxicity in the rat

Paclitaxel is an anticancer drug that has demonstrated severe embryotoxicity in chicks. This embryotoxicity is reduced by liposome encapsulation of the drug. The current study was designed to evaluate the potential of liposome encapsulation for reducing paclitaxel embryotoxicity in rats. Wistar rats were treated with paclitaxel on day 8 of pregnancy (plug = day 0) at doses of 0.67, 2.0, or 10.0 mg/kg intravenously. The same doses of paclitaxel encapsulated in liposomes were administered intravenously to other groups of animals. Control animals were given blank liposomes. Free paclitaxel produced maternal and embryotoxicity at 10.0 mg/kg with three of seven dams dying and resorption of all embryos in surviving dams. Liposome encapsulation at 10.0 mg/kg was not associated with maternal death and there were live fetuses on evaluation at term, although litter size was reduced and malformations occurred in surviving fetuses. At 2.0 mg/kg free paclitaxel, fetal weight was decreased and resorptions increased. Liposome encapsulation at 2.0 mg/kg produced litter results similar to those obtained in control animals given empty liposomes. Malformations were prominent at 2.0 mg/kg free paclitaxel and at 10.0 mg/kg paclitaxel in liposomes and included exencephaly/anencephaly, ventral wall defects, facial clefts, anophthalmia, diaphragmatic hernia, and defects of the kidney, cardiovascular system, and tail. Liposome encapsulation appeared to shift the developmental response to paclitaxel such that 10 mg/kg encapsulated drug produced effects similar to 2.0 mg/kg free drug. These results may have implications for drug delivery of therapeutic agents used during human pregnancy.     

Effects of dihydrotestosterone on bone biochemical markers in sham and oophorectomized rats

Evidence exists to suggest that androgens stimulate bone formation in the estrogen-deficient state, however the mechanism of action is unclear. The following study investigates the effect of dihydrotestosterone (DHT) on biochemical markers of bone turnover and calcium homeostasis in sham and oophorectomized (oophx) rats when either vehicle, 40, 80, or 160 mg/kg body weight (bw) DHT were administered at the time of operation or at 15 weeks postoperation. Serum alkaline phosphatase (ALP) increased following DHT administration in sham and oophx rats in all groups (mean ALP +/- SEM [U/l] week 8; sham vehicle, 40 +/- 7; sham 160 mg DHT/kg bw, 72 +/- 5; oophx vehicle, 60 +/- 6; oophx 160 mg DHT/kg bw, 88 +/- 11) (p < 0.001). In contrast, serum osteocalcin was significantly suppressed in oophx rats administered DHT 15 weeks following operation (mean osteocalcin +/- SEM [micrograms/l] week 8; oophx vehicle, 17.6 +/- 3.5; oophx 160 mg DHT/kg bw, 10.5 +/- 1) (p < 0.01). Urine deoxypyridinoline was significantly decreased when DHT was administered 15 weeks postoophorectomy (p < 0.001); however, urine hydroxyproline was not affected by DHT treatment in any group. Urine calcium was decreased by DHT treatment (mean Ca/Cr +/- SEM week 8; sham vehicle, 0.87 +/- 0.13; sham 160 mg DHT/kg bw, 0.24 +/- 0.08; oophx vehicle, 0.68 +/- 0.16; oophx 160 mg DHT/kg bw; 0.45 +/- 0.1) (p < 0.005) which was associated with an increase in the renal tubular reabsorption of calcium (p < 0.05). This study demonstrates the direct effects of DHT on both bone cell activities and the renal handling of calcium.     

SR 48692, a non-peptide neurotensin receptor antagonist differentially affects neurotensin-induced behaviour and changes in dopaminergic transmission

Unilateral microinjection of neurotensin in the ventral tegmental area of the rat (2.5 micrograms/0.5 microliter) produced behavioural excitation illustrated by contralateral circling. Given orally, SR 48692, a selective and potent non-peptide neurotensin receptor antagonist, significantly reduced these rotations with a triphasic dose-effect relationship. Inhibition occurred at 0.12 mg/kg; further increases in dose up to 2.5 mg/kg produced no significant antagonism, then at doses > or = 5 mg/kg, a second phase of antagonism was observed. Bilateral injection of neurotensin (0.5 microgram each side) into the nucleus accumbens antagonized the increase in locomotor activity following intraperitoneal injection of amphetamine. Given orally, SR 48692 reduced dose-dependently (0.1-1 mg/kg) these intra-accumbens neurotensin effects. Using high pressure liquid chromatography with electrochemical detection, we showed that microgram amounts of neurotensin injected into the ventral tegmental area increased dihydroxyphenylacetate/dopamine ratios in the nucleus accumbens. Using in vivo voltammetry techniques, we found that the injection of nanogram and picogram amounts of neurotensin in the ventral tegmental area stimulated dopamine efflux in the nucleus accumbens. None of these biochemical changes were affected by SR 48692 (0.1-10 mg/kg). These results indicate complex interactions between neurotensin and the mesolimbic dopamine system. More particularly, the differential ability of SR 48692 to affect neurotensin-evoked behavioural versus biochemical changes supports the concept of neurotensin receptor heterogeneity.     

Developmental toxicity evaluation of isopropanol by gavage in rats and rabbits

Timed-pregnant CD (Sprague-Dawley) rats, 25/group, were dosed orally with aqueous isopropanol (IPA; CAS No. 67-63-0) solutions at 0, 400, 800, or 1200 mg/kg/day, once daily on Gestational Days (GD) 6 through 15 at a dosing volume of 5 ml/kg. Artificially inseminated New Zealand white rabbits, 15/group, were dosed orally with IPA at 0, 120, 240, or 480 mg/kg/day once daily on GD 6 through 18 at 2 ml/kg. Maternal body weights, clinical observations, and food consumption were recorded throughout gestation for both species. At scheduled euthanization for both species (GD 20, rats; GD 30, rabbits), fetuses were weighed, sexed, and examined for external, visceral (including craniofacial) and skeletal alterations. For both species, the pregnancy rate was high and equivalent across all groups; no dams or does aborted, delivered early, or were removed from study. In rats, two dams (8%) died at 1200 mg/kg/day and one dam (4%) died at 800 mg/kg/day. Maternal body weights and weight gain were equivalent across all groups, except for statistically significantly reduced gestational weight gain (GD 0-20; 89.9% of control value), associated with statistically significantly reduced gravid uterine weight at 1200 mg/kg/day (89.2% of control value). There were no treatment-related clinical signs or effects on maternal food consumption. All gestational parameters evaluated were equivalent across groups, including pre- and postimplantation loss, fetal sex ratios, and litter size. Twenty-two to 25 litters were examined per group. Fetal body weights per litter were statistically significantly reduced at the two highest doses (97.3 (n.s.), 94.7, and 94.3% of controls at 800 mg/kg/day and 92.1, 91.9, and 95.4% of controls at 1200 mg/kg/day for all fetuses and males and females separately). No evidence of increased teratogenicity was observed at any dose tested in rats. In rabbits, four does (26.7%) died at 480 mg/kg/day. Maternal body weights were statistically significantly reduced during treatment (GD 6-18) at 480 mg/kg/day (45.4% of control value) with a nonsignificant reduction in gestational weight change (GD 0-30; 77.3% of control value) at this dose. Profound clinical signs of toxicity and statistically significantly reduced maternal food consumption were observed at 480 mg/kg/day. All gestational parameters were equivalent across all doses administered. Thirteen to 15 litters were evaluated per group except for the 480 mg/kg/day group with 11 litters (due to maternal deaths). There were no treatment-related effects on pre- or postimplantation loss, fetal sex ratio, litter size, or fetal body weight/litter. Moreover, no evidence was found of increased teratogenicity at any dose tested in rabbits. Therefore, IPA was not teratogenic to CD rats or to NZW rabbits. The NOAELS for both maternal and developmental toxicity were 400 mg/kg/day in rats, and were 240 and 480 mg/kg/day, respectively, in rabbits.     

Science behind total androgen blockade: from gene to combination therapy

Probably the most important finding in the endocrine therapy of prostate cancer is that the testicles and adrenals contribute approximately equal amounts of dihydrotestosterone (DHT), the active androgen that stimulates normal and cancerous prostatic cell growth and function. Structure of the cDNAs and genes encoding most of the enzymes responsible for the transformation of the adrenal precursor dehydroepiandrosterone (DHEA) into DHT have recently been elucidated, namely 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase, 17 beta-hydroxysteroid dehydrogenase, and 5 alpha-reductase. With the action of these enzymes, DHT is then made locally in the prostate from circulating DHEA of adrenal origin. Given such an important role of the adrenals, it is essential to use a pure antiandrogen for maximal blockade of the interaction of DHT with the androgen receptor while the testicles are blocked by orchiectomy or treatment with a luteinizing hormone-releasing hormone (LHRH) super-agonist. This combination therapy was first developed to treat advanced prostate cancer. The multicenter clinical data recently obtained confirm our original data and demonstrate the major importance of the intracrine or in situ formation of androgens in the human prostate from the inactive adrenal steroid precursors. Combination therapy thus permits, for the first time, to prolong life in advanced prostate cancer and, most importantly, offers the possibility of a major improvement in the efficacy of a curative therapy, namely, radical prostatectomy in early stage disease.     

Effect of thyroid hormone on bone and mineral metabolism in rat: evaluation by biochemical markers

We evaluated the effects of the thyroid hormone on bone and mineral metabolism in rats using biochemical markers [pyridinoline (Pyr), deoxypyridinoline (Dpyr), Osteocalcin (OC), alkaline phosphatase (Alp)] and the measuring of bone mineral density (BMD). First, the rats were divided into three groups: 1) control group 2) The fifty micrograms group (T3-50) [It was given 50 micrograms/kg ip/day of triiod-l-thyronine (T3) for 2 weeks.] 3)The hundred micrograms group (T3-100) [It was given 100 micrograms/kg ip/day of T3 for 2 weeks.] Next, the rats were divided into two groups: 1)control group and 2)T3 group. The latter was given 100 micrograms/kg of T3 ip/day for 4 weeks. In experiment 1, Pyr and Dpyr levels in the T3 groups were significantly higher or well tended to be higher than those in the control group. OC levels in the T3 groups were significantly higher than in the control group until day 7. The Z-score of Pyr and Dpyr in T3-100 were two to thirteen times higher than those of OC and Alp. In experiment 2, Pyr and Dpyr levels in the T3 group were significantly higher or well tended to be higher than those in the control group. OC levels in the T3 group were significantly higher than those in the control group only on day 3. In the present study, the administering of T3 100 micrograms decreased both cortical (tibia) and trabecular (lumbar spine) BMDs in the rats. Bone resorption continued to increase after increased bone formation was reduced by T3 administration. Furthermore, bone resorption exceeded bone formation throughout T3 administration.     

Ribavirin potentiates the efficacy and toxicity of 2',3'- dideoxyinosine in the murine acquired immunodeficiency syndrome model

The efficacy and toxicity of ribavirin (25 or 125 mg/kg/day), 2',3'-dideoxyinosine (ddI) (200 mg/kg/day) and a combination of both drugs at these doses given for 6 weeks were investigated in the murine acquired immunodeficiency syndrome model. Our results showed a significant protection against splenomegaly, lymphadenopathy and hypergammaglobulinemia in mice treated with ribavirin at 25 mg/kg/day alone or in combination with ddI at 200 mg/kg/day. A good synergistic effect was observed with the drug combination, whereas ddI alone (200 mg/kg/day) did not give any protection. Ribavirin/ddI combination protected against the loss of CD8 T cells in spleen and restored the capacity of splenocytes to proliferate after activation with a mitogenic agent. Moreover, the drug combination resulted in a protection of the spleen and cervical lymph node architectures and a regression of germinal centers. Hematotoxicity appeared at a dose of 125 mg/kg of ribavirin alone and increased when used concomitantly with ddI. In conclusion, ribavirin and ddI at low doses are synergistic and effective in the murine acquired immunodeficiency disease model, but at high doses they are toxic.     

Characteristics of target-reaching in cats. III. Lifting and protraction with an obstacle in the movement path and after its removal

We have established a rat model that reflects the course of development of alcohol and opiate addiction. The present study with d-amphetamine aimed to define general principles in the development of an addiction. Male rats had a continuous free choice between d-amphetamine solutions (100, 200 and 400 mg/l) and water for 47 weeks. An initial intake of high doses of d-amphetamine during the first weeks of drug choice was followed by an individually stable pattern of drug consumption of moderate drug doses. During this period of controlled consumption (from week 10 to week 40), the voluntary intake of d-amphetamine depended on individual factors (dominant rats: 0.37+/-0.02 mg/kg per day, subordinate rats: 0.57+/-0.05 mg/kg per day) and environmental variables (group housing: 0.21+/-0.02 mg/kg per day, single housing: 0.41+/-0.03 mg/kg per day). Beginning with week 41, voluntary d-amphetamine consumption progressively increased (1.9+/-0.2 mg/kg per day in week 47), although the experimental conditions remained unchanged. Drug intake during a retest (free choice as before) after 6 months of drug deprivation revealed that the rats had persistently lost their control over drug intake and were no longer able to adjust drug taking to internal and external conditions. These addicted rats took very high drug doses, even when all d-amphetamine solutions but not water were adulterated with bitter tasting quinine (6.6+/-0.6 mg/kg per day; age-matched controls: 0.37+/-0.04 mg/kg per day). Forced intake of d-amphetamine for 47 weeks (7.1+/-0.3 mg/kg per day) via the drinking fluid caused physical dependence (hyperreactivity during withdrawal) but did not lead to drug addiction (voluntary intake in the retest with adulteration: 0.42+/-0.04 mg/kg per day). Both the temporal development and the prerequisites of psychostimulant addiction were in principle the same as for alcohol and opiates.