Avril McMahon

Sperm Chromatin Structure Is Altered in Cynomolgus Monkeys With Environmentally Relevant Blood Lead Levels

Exposure to lead has been associated with a variety of adverse reproductive outcomes such as spontaneous abortion, impaired fecundity, and sterility. Although decreased sperm counts and serum testosterone levels have been found in men with occupational lead exposure, animal experiments suggest that fertility may be impaired at blood lead levels that have no apparent effect on reproductive hormone levels or sperm concentration. Consequently, this study investigated the effect of chronic lead treatment on semen quality in healthy cynomolgus monkeys aged 15- 20 years with mean (± SD) blood lead levels of 10 ± 3 μg/dL (range 6-20 μg/dL, n = 4) and 56 ± 49 μg/dL (range 22-148 μg/dL, n = 7) compared to a reference group with blood lead levels <1.0 μg/dL (n = 8). Blood and semen samples were collected once from each monkey in five different months. Serum testosterone levels were determined by radioimmunoassay, and lead effects on chromatin structure were analyzed by flow cytometry. There were no effects of treatment on circulating levels of testosterone or parameters of semen quality such as sperm count, viability, motility, and morphology. However, significant (p < 0.03) treatment-related effects were seen on SD αt values in the treated vs control animals. Group comparisons also revealed that the effects of chronic lead exposure were significant (p < 0.05)

Reproductive endocrine effects of chronic lead exposure in the male cynomolgus monkey

The reproductive endocrine effects of chronic lead exposure were investigated in 9 year old male (n = 16) cynomolgus monkeys, orally dosed with lead acetate (1500 micrograms/kg/day) according to the following dosing regimens: continuous exposure from birth onward (lifetime, n = 4), beginning at postnatal day 300 (post-infancy, n = 5) and postnatal days 0 to 400 (infancy, n = 4), or vehicle only (control, n = 3). Altered Sertoli cell function was shown by a significant (P = 0.0286) decrease in the inhibin/follicle stimulating hormone (INH/FSH) ratio in both the lifetime and post-infancy groups compared to the control group. Gonadotropin releasing hormone (GnRH) stimulated levels of luteinizing hormone (LH) were significantly (P = 0.0370) lower in the lifetime group compared to the control group as determined by comparisons of the area under the curve. These data suggest that chronic lead exposure exerts a subtle effect on the pituitary as well as on Sertoli cell function.

Hexachlorobenzene toxicity in the monkey primordial germ cell without induced porphyria

Hexachlorobenzene is a persistent chlorinated organic chemical that has been detected in many tissues from a variety of species including human ovary and human ovarian follicular fluid. When administered in high dosage to nonhuman primates, hexachlorobenzene causes destruction of ovarian primordial germ cells in association with systemic toxicity. The purpose of these experiments was to assess relative ovarian germ cell sensitivity at much lower dosages of hexachlorobenzene that do not produce systemic effects and additionally to evaluate oocyte function by means of the response to superovulation, fertilization, and embryo cleavage during a cycle of in vitro fertilization in the cynomolgus monkey. Hexachlorobenzene in dosages of 0.1, 1.0, and 10.0 mg/kg/day was administered orally by gelatin capsule for 90 days. There was a dose-dependent accumulation of HCB in serum and other tissues without any change in the serum estradiol response to human menopausal gonadotropin, oocyte recovery, oocyte maturation, oocyte fertilization in vitro, and early embryo cleavage rate. There was a dose-related toxic effect observed in primordial germ cells at the lowest dose despite no evidence of systemic or hepatic effects. As there were no changes in the urinary porphyrin excretion, the mechanism of hexachlorobenzene ovotoxicity may be distinct from hexachlorobenzene-induced cytochrome P-450-dependent inhibition of uroporphobilinogen decarboxylase in the liver, although such intraovarian metabolism cannot be excluded.

Alterations in circulating ovarian steroids in hexachlorobenzene-exposed monkeys

Hexachlorobenzene (HCB) is a global pollutant that has been identified in human serum and ovarian follicular fluid, and its effect on ovarian function has not been adequately defined. Thus, the effects of HCB on ovarian steroidogenesis and menstrual cycle characteristics were investigated in cynomolgus monkeys (n = 16) orally dosed by gelatin capsule (0.0, 0.1, 1.0, and 10.0 mg HCB/kg b.wt./d) for 90 d (approximately three menstrual cycles). Analysis of change in menstrual cycle length for each animal revealed a dose-dependent increase (P = 0.02) in cycle length. Ovulatory levels of estradiol (E2) were significantly reduced (P = 0.02) in the highest treatment group. During ovulation induction, the area under the E2 concentration curve (AUC) was significantly (P = 0.03) suppressed in the highest treatment group. Our data demonstrate that HCB treatment, under the conditions of the present study, alters both ovarian function and menstrual cycle characteristics with a no observable adverse effect level of 1.0 mg/kg.

The influence of dietary isoflavone on the uterotrophic response in juvenile rats

Current in vivo methods to identify and assess reproductive hazards of endocrine disrupting substances are often confounded by the presence of isoflavones (genistein, diadzein, glycitein), strongly hormonally-active substances, in the diet of laboratory rodents. However, studies that have attempted to study the influence of dietary isoflavone on qualitative and quantitative uterotrophic responses have been limited by the few doses of isoflavone tested, stress to the animals due to changing of the diet immediately prior to testing and/or comparing effects of diets of very different composition. The current study examined the effects of isoflavone on uterotrophic response by using immature female rats reared from conception on diets varying only in the amount of isoflavone concentrate (Novasoy) added to a virtually isoflavone-free soya-based diet. The effects of these diets, and a soya-free semipurified diet (AIN 93G) on uterotrophic responses to treatment with a strong (Ethinyl Estradiol, EE) or a weak (bisphenol A, BPA) estrogenic substance were examined. The pups were treated with subcutaneous injections of either EE (1 microg/kg/day), BPA (600 mg/kg/day) or corn oil (vehicle) control for 3 days starting at weaning on post natal day (PND) 21. On the morning of PND 24 pups were sacrificed and uterus weight, epithelium labeling index (Bromo deoxyuridine incorporation), uterine epithelium thickness, and peroxidase activity were determined. Diet did not influence unstimulated uterine weight, epithelial height or peroxidase activity except at the highest isoflavone diet where animals had significantly increases in all three endpoints. Uterine weight, epithelial thickness and peroxidase were all significantly increased by EE or BPA treatment. There was no evidence of diet-induced potentiation or inhibition of the stimulatory actions of either EE or BPA on either uterine weight or epithelial thickness while EE-induced increase in uterine peroxidase activity was increased synergistically by the highest dose of isoflavone. A similar response to the latter effect was seen in BPA treated animals although this response was not significantly different from that of BPA treated rats fed the isoflavone-free soy diet. The rate of endometrial epithelium labeling with BrdU was not altered by any treatment. These results indicate that dietary isoflavone content can directly influence uterine weight and other estrogen-dependent endpoints demonstrating the potential of these to reduce the active range of the uterotrophic assay. However, there is no indication that isoflavones impair or potentiate the stimulatory action of either strong (EE) or weaker (BPA) estrogen agonists on uterine weight or epithelial morphology although the data do suggest the potential for synergy between high isoflavone content and estrogen agonist in inducing uterine peroxidase.

The agonist (d-leu-6,des-gly-10)-LHRH-ethylamide does not protect the fecundity of rats exposed to high dose unilateral ovarian irradiation☆

Attempts to protect the ovary from the toxic effects of radiation and chemotherapy are relevant to the management of the young patient with cancer. Previous studies in a variety of animal species with several types of agonists of GnRH have shown promise in affording gonadal protection using indirect indices of reproductive function. The current investigations are based on these observations. Female rats were treated with (d-leu-6,des-gly-10) LHRH-ethylamide (GnRHa) from day 22 to day 37 of life. Sham-irradiation or unilateral irradiation of the left ovary was performed on day 30. The animals were mated following resumption of cycles and sacrificed on day 21 of pregnancy. There was no significant effect of ovarian artery ligation. Radiation reduced ovarian function ipsilateral to the radiation. GnRHa alone did not affect reproductive performance significantly. GnRHa and radiation combined resulted in no reproductive protection but augmented the damage done to the ipsilateral ovarian weight and to numbers of corpora lutea and fetuses. Under these experimental circumstances the agonist provided no protection.