Sex difference in the metabolism of pirmenol in rats

The in vitro metabolism of pirmenol (cis-alpha-[3-(2,6-dimethyl-1-piperidinyl)propyl]-alpha-phenyl-2-pyri dinemethanol) and glucuronidation of its metabolites, a 4-hydroxylated derivative of pirmenol (M3) and 3-methylether of M3 (M5), were investigated using a hepatic 9000 x g supernatant and microsomes, respectively, of female and male rats in order to elucidate the higher urinary excretion of M3G and M5G (glucuronides of M3 and M5, respectively) in females previously observed in in vivo metabolism. Pirmenol delta1' iminium ion (M2) and M3 were formed by the oxidation of pirmenol in both sexes; however, M2 was the main metabolite in males, while M2 and M3 were formed at nearly the same level in females. On glucuronidation of M3 and M5, the Vmax values of both compounds were higher in female rats, consistent with the results in vivo. In addition, the sex difference in the urinary excretion ratio of M5G to M3G (1.1 in female, 2.5 in male) might reflect the lower availability of M3 for glucuronidation in male rats in vivo. The chromatographic separation of diastereomers of M5G was also described.     

8-[18F]fluorooctanoic acid and its beta-substituted derivatives as potential agents for cerebral fatty acid studies: synthesis and biodistribution

Fluorine-18 labeled analogs of 8-fluorooctanoic acid and its structurally modified derivatives with methyl or gem-dimethyl branching or with oxygen substitution at the C3 position were prepared using nucleophilic substitution of the tosylate precursors by [18F]fluoride ion, for evaluation as tracers for cerebral fatty acid metabolism. Tissue distribution studies in rats showed low brain uptakes of these 18F-labeled fatty acid analogs with poor brain-to-blood ratios of activity. The oxygen-substituted analog did not show any significant accumulation of radioactivity in most tissues. The initial brain uptake of activity after injection of ethyl 8-[18F]fluorooctanoate and its free acid remained virtually unchanged over an extended time period, beta-Monomethyl and beta-gem-dimethyl branched analogs had similar brain uptake at the early time period, but they showed rapid clearance of activity from the brain. TLC analysis showed no incorporation of 8-[18F]fluorooctanoic acid and its beta-dimethyl analogs into brain lipids. It was also shown in the metabolite analysis that the labeled metabolites produced from 8-[18F]fluorooctanoic acid are found in blood, and that they could enter the brain to a significant degree. On the contrary, such radioactive metabolites could not be found in the brain in the experiment with the beta-gem-dimethyl branched analog. Thus, the present studies showed that retention of radioactivity in the brain with 8-[18F]fluorooctanoic acid derivatives is mainly attributable to their radioactive metabolites, and that the rapid clearance of beta-branched analogs from the brain is due to the lack of availability as substrates in the cerebral fatty acid metabolism.     

Drug metabolism and morphologic changes in the liver of nafenopin-treated rats

Nafenopin (2-methyl-2[p-(1,2,3,4-tetrahydro-1-naphthyl) phenoxy] propionic acid), a phenolic ether with hypolipidemic properties, given to rats of both sexes for 3 or 14 days, caused an increase in liver weight, peroxisome (microbody) proliferation and smooth endoplasmic reticulum accumulation in hepatocytes. In females, 3 days of nafenopin administration elicited a significant reduction of zoxazolamine paralysis time and an enhancement of its metabolism by the 9,000 g supernatant fraction of the liver. In contrast, treatment of males resulted in a prolongation of paralysis and a decrease of zoxazolamine hydroxylation. The serum cholesterol and triglyceride levels were not changed by short-term administration of the hypolipidemic drug to female rats, but there was a lowering of triglycerides in the males. Given for 14 days, nafenopin reduced paralysis time to the same extent in both sexes. The in vitro metabolism of zoxazolamine was similar to that observed after short-term nafenopin administration. A significant fall in serum triglycerides was noted in both females and males. The sex difference in zoxazolamine metabolism was not dependent on endogenous testosterone.     

Leptin is not necessary for gestation and parturition but regulates maternal nutrition via a leptin resistance state

Leptin levels are significantly elevated in pregnant mice, rats and humans suggesting a critical role for leptin during gestation. To address whether leptin plays a putative role in the physiology of pregnancy, we asked whether a mouse pregnancy would be affected by the complete absence of leptin from both the mother and fetuses. Thus, leptin-deficient ob/ob females were first treated with exogenous leptin and then mated to similarly treated ob/ob males. All resulting fetuses have an ob/ob genotype and lack like their mothers any endogenous leptin production. Withdrawal of leptin treatment at 0.5, 6.5, 10.5 and 19.5 days p.c. did not affect any stage of the pregnancy despite a gradual return of the mothers to an obese state. However, some mice had delayed gestation periods of 21-23 days which were associated with prolonged parturition. The pups were normally delivered with no obvious signs of deformities although none survived beyond a day after delivery due to failure of lactation. Monitoring daily food intake of pregnant ob/ob females treated throughout gestation with leptin revealed significantly elevated levels of food intake from day 10 p.c. and onward demonstrating an attenuation of a leptin response during pregnancy and a leptin resistance effect. These studies demonstrate that in the mouse, leptin is not a critical molecule for implantation, gestation, fetal growth and parturition but that the leptin resistance effect at mid-gestation aims to stimulate food intake thus providing sustained energy resources for pregnancy.     

Role of brain allopregnanolone in the plasticity of gamma-aminobutyric acid type A receptor in rat brain during pregnancy and after delivery

The relation between changes in brain and plasma concentrations of neurosteroids and the function and structure of gamma-aminobutyric acid type A (GABAA) receptors in the brain during pregnancy and after delivery was investigated in rats. In contrast with plasma, where all steroids increased in parallel, the kinetics of changes in the cerebrocortical concentrations of progesterone, allopregnanolone (AP), and allotetrahydrodeoxycorticosterone (THDOC) diverged during pregnancy. Progesterone was already maximally increased between days 10 and 15, whereas AP and allotetrahydrodeoxycorticosterone peaked around day 19. The stimulatory effect of muscimol on 36Cl- uptake by cerebrocortical membrane vesicles was decreased on days 15 and 19 of pregnancy and increased 2 days after delivery. Moreover, the expression in cerebral cortex and hippocampus of the mRNA encoding for gamma2L GABAA receptor subunit decreased during pregnancy and had returned to control values 2 days after delivery. Also alpha1, alpha2, alpha3, alpha4, beta1, beta2, beta3, and gamma2S mRNAs were measured and failed to change during pregnancy. Subchronic administration of finasteride, a 5alpha-reductase inhibitor, to pregnant rats reduced the concentrations of AP more in brain than in plasma as well as prevented the decreases in both the stimulatory effect of muscimol on 36Cl- uptake and the decrease of gamma2L mRNA observed during pregnancy. These results indicate that the plasticity of GABAA receptors during pregnancy and after delivery is functionally related to fluctuations in endogenous brain concentrations of AP whose rate of synthesis/metabolism appears to differ in the brain, compared with plasma, in pregnant rats.     

Hormonal interaction with stimulus situational factors in the initiation of maternal behavior in nonpregnant rats.

Previous hormonal studies have identified the hormonal and stimulus factors mediating the initiation of maternal behavior but have failed to reduce hormone-induced latencies of nonpregnant females to less than 1–2 days of continuous pup exposure. For the purpose of testing whether this delay is due to an olfactory-vomeronasal-mediated aversive reaction to pups like that found in untreated virgins, in 3 experiments estrogen-injected hysterectomized-ovariectomized (HO-EB) nonpregnant Charles River CD females were subjected to olfactory-vomeronasal deafferentation. Findings indicate that after HO-EB treatment, tendencies to initially avoid pup contact remain strong. Next, the hypothesis was explored that experiences during late pregnancy and/or parturition interact with hormonal priming to modify pup avoidance. Nonpregnant HO-EB females that had been exposed to pregnant-parturient females for 2 wks were tested under conditions simulating parturition. A high percentage rapidly initiated maternal behavior, but conditions during testing proved more important than prior exposure to pregnancy/parturition. Hormonally treated but not sham-treated females initiated maternal behavior most rapidly when first exposed to 1 newborn in the nest during the light phase. Prepartum caesarean-delivered females, however, responded maternally to 4 3–8 day old pups outside the nest, which indicates that additional factors operate at parturition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reproductive state changes NADPH-diaphorase staining in the paraventricular and supraoptic nuclei of female rats

It has been demonstrated in guinea pigs that nitric oxide synthase (NOS) activity is increased in late pregnancy in some peripheral tissues and in the cerebellum. To determine whether similar changes would be observed in areas of the brain known to play a role in parturition, staining for NADPH-diaphorase, a histochemical marker of NOS synthase, in the paraventricular (PVN) and supraoptic nuclei (SON) was compared among ovariectomized, virgin and late pregnant rats. The number of cells showing dense staining for NADPH-diaphorase increased in both the SON and PVN in late pregnancy compared to that observed in virgin and ovariectomized females. Thus, changes in reproductive state are associated with changes in NADPH-diaphorase staining in areas of the brain that are intimately involved in the control of reproductive function.     

Effect of tamoxifen feeding on metabolic activation of tamoxifen by the liver of the rhesus monkey: does liver accumulation of inhibitory metabolites protect from tamoxifen-dependent genotoxicity and cancer?

Tamoxifen induces hepatocellular carcinomas in rats and is converted by rat hepatic cytochrome P450 enzymes into reactive metabolites capable of forming adducts with nucleic acids, proteins and chromosomal aberrations. In rats tamoxifen has also been shown to induce liver cytochrome P450 enzymes, to stimulate its own metabolism leading to greater covalent binding and to induce a higher degree of unscheduled DNA synthesis. This suggests that, at least in the rat, a sensitive species, tamoxifen may contribute significantly to its genotoxic and carcinogenic potential, by assisting its own metabolic activation. We have now investigated the effect of feeding tamoxifen to male and female Rhesus monkeys. A marked induction of the hepatic cytochrome(s) P450 is found in the monkey but, in spite of this, the in vitro metabolism of 7-ethoxyresorufin by microsomes from treated animals is markedly inhibited and so is the dealkylation of two other 7-alkoxyresorufin substrates. Evidence is presented for the accumulation in the liver of monkeys treated with tamoxifen of a powerful inhibitor of drug metabolism, and the inhibitor is identified as a metabolite of tamoxifen, its N,N-didesmethyl derivative. The level of 32P-postlabelled DNA adducts was considerably higher in rats given tamoxifen than in similarly treated monkeys. Also, whereas rats responded to tamoxifen treatment with a marked increase in covalent binding to microsomal protein, in the monkeys, where accumulation of the inhibitory metabolite in the microsomal fraction was also seen, covalent binding was not greater with microsomes from treated animals than in the corresponding controls. N,N-Didesmethyl-tamoxifen, added in vitro to human and rat microsomes, reduced significantly the extent of covalent binding, suggesting that the accumulation of the metabolite observed in the liver of primates may discourage the cytochrome P450-dependent conversion of tamoxifen into reactive derivatives and in this way protect against the formation of adducts. This mechanism may also contribute to protecting the primate against tamoxifen- induced liver cancer.     

Changes in prostaglandin F and 13,14-dihydro-15-keto-prostaglandin F concentrations in amniotic fluid at the onset of and during labour

Concentrations of prostaglandin F (PGF) and its major circulating metabolite 13,14-dihydro-15-keto-PGF (PGFM) have been measured in amniotic fluid during spontaneous labour at term. Levels of both PGF and PGFM were significantly higher during early spontaneous labour, at a cervical dilatation of less than 4 cm, than before the onset of labour. Patients who started labour spontaneously but later required oxytocin therapy for failure to progress in first stage had lower levels of PGF and PGFM than patients who progressed adequately without oxytocin therapy. During spontaneous labour, concentrations of both PGF and PGFM increased significantly with advancing cervical dilatation. These indicate that the accumulation of prostaglandins in amniotic fluid during labour is not due to decreased metabolism. They furthermore provide the strongest evidence available so far for an increase in intrauterine prostaglandin synthesis during human parturition.     

Communal reproductive success in rats (Rattus norvegicus): Effects of group composition and prior social experience.

Compared the reproductive success and maternal behavior of sibling pairs of female Long-Evans rats (Rattus norvegicus) housed together from birth (familiar) to that of pairs of unrelated females housed apart during development (unfamiliar). Sires either remained in the colonies through weaning of their pups or were removed before parturition. Familiar animals reared more pups to weaning, were more likely to share in caring for pups, and were less likely to exhibit infanticide than were unfamiliar ones. The presence of males in cages with pups had no direct effect on the reproductive success of females, but female pairs housed with males spent less time than female pairs housed alone caring for pups together in a combined nest. Conflicting evidence for communal rearing in populations of wild rats may reflect differences in the genetic relatedness or early social experience of female rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pharmacokinetic study of nerisopam and its n-acetyl metabolite in rats

Three doses were administered to the rats during the pharmacokinetic study of nerisopam and the plasma concentrations of nerisopam and its N-acetyl metabolite were determined parallelly by means of validated SPE-HPLC method developed by the authors. The pharmacokinetics of nerisopam could be described by a two-compartment open model in rats, it was absorbed rapidly and could be measured in plasma for about 8 hours. The peak plasma concentration of the N-acetyl metabolite was reached rapidly a little bit later than that of the parent compound, similarly to the human plasma, and it could be measured for about 12 hours. The pharmacokinetics of N-acetyl metabolite could be described by an one-compartment open model. The fast appearance of the metabolite and the Cmax and AUC 0-infinity values higher than those of nerisopam refer to an intensive "first-pass" metabolism. The AUC-dose curves indicate that supposingly the mechanism transforming the N-acetyl metabolites are not as fast as the acetylation.     

Gender differences in acute N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA) nephrotoxicity in Fischer 344 rats

N-(3,5-Dichlorophenyl)succinimide (NDPS) is an agricultural fungicide that induces nephrotoxicity as its major toxicity. NDPS is also a more potent nephrotoxicant in female than in male rats. The purpose of this study was to examine the nephrotoxic potential of the two NDPS metabolites N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA) in age-matched male and female Fischer 344 rats to determine if gender differences exist for the nephrotoxicity induced by the two NDPS metabolites. Rats (4 per group) were administered a single intraperitoneal (ip) injection of NDHS or 2-NDHSA (0.025 or 0.05 mmol/kg) or vehicle, and renal function was monitored for 48 h. Neither compound induced significant nephrotoxicity in male rats at the doses tested. However, in female rats both metabolites induced marked nephrotoxicity at the 0.05 mmol/kg dose level, and treatment with 0.025 mmol/kg 2-NDHSA induced some changes in renal function (transient diuresis, transient proteinuria, decreased organic ion accumulation). Little effect on renal function was induced in females by treatment with 0.025 mmol/kg NDHS. At toxic levels in female rats, the renal lesions were located primarily in the S2 and S3 segments of the proximal tubule. These results indicate that, like the parent compound, gender differences exist in the nephrotoxic potential of NDHS and 2-NDHSA. The results also suggest that in females, as in males, NDPS nephrotoxicity is mediated via NDHS and/or 2-NDHSA. However, it is not clear if the ultimate nephrotoxicant species following NDPS exposure is different in males and females or if the same ultimate nephrotoxicant species is produced in both species but handled differently by male and female kidneys. Thus, further studies are needed to determine the exact nature of the ultimate nephrotoxicant species and the mechanisms of the observed gender differences.     

In vitro and in vivo metabolism of the progestagen Org 30659 in several species

The metabolism of Org 30659 [(17alpha)-17-hydroxy-11-methylene-19-norpregna-4, 15-dien-20-yn-3-one], a new potent progestagen currently under clinical development by NV Organon for use in oral contraceptive and hormone replacement therapy, was studied in vivo after oral administration to rats and monkeys and in vitro using rat, rabbit, monkey, and human liver microsomes and rat and human hepatocytes. After oral administration of [7-3H]Org 30659 to rats and monkeys, Org 30659 was extensively metabolized in both species. Fecal excretion appeared to be the main route of elimination. In rats, opening of the A-ring, resulting in a 2-OH,4-carboxylic acid, 5alpha-H metabolite of Org 30659, was the major metabolic route in vivo. Other metabolic routes involved the introduction of an OH group at C15beta, followed by a shift of the Delta15-double bond to a 16/17-double bond with subsequent removal of the OH group at C17 and reduction of the 3-keto,Delta4 moiety followed by sulfate conjugation of the 3-OH substituent. These metabolic routes observed in vivo were also major routes in incubations with rat hepatocytes. In rat liver microsomes, Org 30659 was metabolized by reduction of the 3-keto,Delta4 moiety. Rat hepatocyte incubations with Org 30659 were more representative of the in vivo metabolism of Org 30659, compared with rat microsomal incubations. Both in vitro and in vivo, the majority of the metabolites were 3alpha-OH,4,5alpha-dihydro derivatives. In monkeys, Org 30659 was mainly metabolized at the C3- and C17-positions in vivo. The 3-keto moiety was reduced to both 3beta-OH and 3alpha-OH substituents. In addition to phase I metabolites, glucuronic acid conjugates were observed in vivo. In monkey liver microsomes, the 6beta-OH metabolite of Org 30659 was the major metabolite present. Similar to the monkey liver microsomes, rabbit and human liver microsomes converted Org 30659 to the 6beta-OH metabolite. This metabolite was also the major metabolite in incubations with human hepatocytes.     

Sex differences in nitrite/nitrate levels and antioxidant defense in rat brain

This study assessed sex differences in stable metabolites of nitric oxide and major enzymes involved in antioxidant defense in various regions of rat brain. Nitrite/nitrate levels and activities of superoxide dismutase and catalase were determined in cortex, hippocampus, corpus striatum, midbrain and cerebellum of adult male and female Sprague-Dawley rats. Nitrite/nitrate levels were significantly higher in the cortex and the hippocampus of male than female rats, while catalase activity was higher in the cortex of females than in males. These sex differences may have significant effects on brain function in health and disease.     

Interactions of contact, odor cues, and androgens in strange-male-induced early pregnancy disruptions in mice (Mus musculus).

Novel males can disrupt early pregnancy in female house mice (Mus musculus). In Experiment 1, exposure to novel males disrupted pregnancy, but exposure to male urine did not. In Experiment 2, urine from male or female mice or rats painted on females' noses did not influence pregnancy. In Experiment 3, the conjunction of urine painted on female's noses and vulval stimulation did not affect pregnancy more than water with similar stimulation. In Experiment 4, males housed above females were separated from them by a wire mesh grid; intact males disrupted pregnancy, but castrated ones did not. In Experiment 5, such housing of castrated males or ovariectomized females produced a strong disruption of pregnancy if the stimulus animal was given testosterone but not if it was given oil injections. In Experiment 6, transfers of odorous emissions failed to disrupt pregnancy. Contact and androgen activity are necessary for strange males to disrupt pregnancy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in EEG in adult gonadectomized rats before and after hormonal treatment

EEG activity was recorded from the left and right parietal cortex in adult male and female Wistar rats that were gonadectomized (GNX) after puberty during 2 days without and 3 days with hormonal treatment (either testosterone propionate, 5 alpha-DHT or vehicle in males and progesterone, estradiol benzoate or vehicle in females). In contrast to EEG characteristics reported for intact rats, GNX abolished right over left parietal activation in both sexes and, sex differences in EEG interhemispheric correlation and in theta and delta relative power in the right parietal; additionally GNX males showed higher absolute power than females. Hormonal treatment reestablished interparietal asymmetry in both sexes and a lack of sex differences in absolute power, however, it was not enough to reestablish sex differences in delta and theta proportion in the right parietal nor in interhemispheric correlation. Differential effects were obtained with testosterone propionate and 5 alpha-DHT in males suggesting that activational effects of testosterone on EEG are probably exerted through testosterone or its aromatized metabolites. The results of our study indicate that the activational effects of gonadal steroids after puberty are necessary for maintaining sex differences in the EEG of the adult rat.     

In vivo effects of remoxipride and aromatic ring metabolites in the rat

The in vivo effects of remoxipride, in relation to some of its identified metabolites, were investigated in adult male Sprague-Dawley rats. The methods used included: (1) estimation of the in vivo rate of brain monoamine synthesis by measuring the accumulation of dihydroxyphenylalanine and 5-hydroxytryptophan after decarboxylase inhibition; (2) observations of spontaneous locomotor activity in a photocell-equipped open-field arena ( approximately 0. 5 m2); (3) treadmill locomotion ( approximately 4 m min-1); (4) inclined grid (60 degrees ) catalepsy test; (5) d-amphetamine-induced (1.0 mg kg-1) hyperlocomotion;(6) quinpirole-induced (0.4 mg kg-1) hypothermia. By use of one or more of these tests, the findings with remoxipride were as follows: First, remoxipride had a late onset of action (up to 3 h). Second, potency and efficacy depended on exposure to hepatic metabolism. Thus, intraperitoneal administration was more effective than the subcutaneous route, whereas virtually all biological effects were lost on intracerebroventricular administration. The ED50 values (micromol kg-1, neostriatal dihydroxyphenylalanine accumulation) for remoxipride and a range of its phenolic aromatic ring metabolites were: remoxipride (approximately 20), NCQ-344 (approximately 0.01), FLA-797 (approximately 0.1), FLA-908 (approximately 2.2), NCQ-436 (approximately 25) and NCQ-469 (approximately 30). Considering remoxipride as a nonclozapine atypical antipsychotic drug, together with the fact that remoxipride behaves as a prodrug in the laboratory studies above, further characterization of the pharmacodynamic profile of its metabolites remains a challenge.