We tested the hypothesis that progesterone (P(4)) acts at a local level to inhibit luteal apoptosis. Initial experiments employed aminoglutethimide, a P450 cholesterol side-chain cleavage inhibitor, to inhibit steroid synthesis. Cultured bovine luteal cells were treated with aminoglutethimide (0.15 mM) +/- P(4) (500 ng/ml) for 48 h. Luteal cells were recovered and snap frozen for isolation and analysis of oligonucleosomal DNA fragmentation or fixed for morphological analysis. Medium was collected for analysis of P(4) levels by RIA. Aminoglutethimide inhibited P(4) synthesis by > 95% and increased the level of apoptosis as evidenced by (32)P-labeled oligonucleosomal DNA fragmentation (> 40%). P(4) supplementation inhibited the onset of apoptosis that was induced by aminoglutethimide. These data were further supported by morphological assessment of apoptotic cells utilizing a Hoechst staining technique and together strongly suggest that P(4) has anti-apoptotic capacity. Using reverse transcription-polymerase chain reaction, we were able to isolate a 380-base pair cDNA from the bovine corpus luteum (CL) that was 100% homologous to the progesterone receptor (PR) previously found in bovine oviductal tissue. Furthermore, PR transcripts were present in large and small luteal cells. Immunohistochemistry also revealed that PR protein was present in both large and small luteal cells. To determine whether the anti-apoptotic effect of P(4) was regulated at the receptor level, luteal cells were cultured in the presence of PR antagonists, RU-486 and onapristone, for 48 h. Both antagonists caused approximately a 40% increase in (32)P-labeled oligonucleosomal DNA fragmentation. Interestingly, there was no difference (P >/= 0.05) in P(4) levels after treatment with PR antagonists. These observations support the concept that P(4) represses the onset of apoptosis in the CL by a PR-dependent mechanism.

At the biomedical, regulatory, and public level, considerable concern surrounds the concept that inappropriate exposure to endocrine-disrupting chemicals, especially during the prenatal and/or neonatal period, may disrupt normal reproductive tract development and adult function. The intent of this review was to 1. Describe some unique advantages of the hamster for perinatal endocrine disruptor (ED) studies, 2. Summarize the morphological and molecular consequences of exposure to the established perinatal ED, diethylstilbestrol, in the female and male hamster, 3. Present some new, histomorphological insight into the process of neonatal diethylstilbestrol-induced disruption in the hamster uterus, and 4. Introduce recent efforts and future plans to evaluate the potency and mechanism of action of other putative EDs in the hamster experimental system. Taken together, the findings indicate that the hamster represents a unique and sensitive in vivo system to probe the phenomenon of endocrine disruption. The spectrum of candidate endpoints includes developmental toxicity, neoplasia, and more subtle endpoints of reproductive dysfunction.

Prenatal and neonatal exposure to natural and synthetic estrogens induces developmental abnormalities in the male and female reproductive systems in several species. In hamsters, a single injection of diethylstilbestrol (DES) on the day of birth induces teratogenic and neoplastic changes throughout the female reproductive tract, apparently via a direct mechanism. The present study investigated the extent and specificity of this phenomenon in the male reproductive system. Male golden hamsters received injections of DES or estradiol-17beta (E2; 100 microg/ animal) on the day of birth and were then killed at 42 (pubertal) and 90 (adults) days of age. Blood was collected for serum testosterone analysis, and the testes and accessory organs were weighed and examined histologically. At the pubertal stage, testicular and accessory organ weights plus serum testosterone levels were similar in untreated animals and in both groups of estrogen-treated animals. Also at the pubertal stage, initiation of spermatogenesis appeared normal in both groups of estrogen-treated animals. In contrast, 100% of the DES-treated animals (n = 22) but none of the E2-treated animals exhibited multiple lesions in the reproductive tract as adults. These DES-induced lesions included cryptorchidism with the testes attached to the abdominal wall, solid testicular tumors, multiple epididymal cysts, and involution of accessory organs. Spermatogenesis was disrupted in the seminiferous tubules, with no developing germ cells, and the interstitial cells were organized as a sheath around the dysfunctional tubules. The epididymis had an involuted epithelial layer with a preponderance of multi-nucleated cells, and seminal vesicle morphology was also abnormal. These DES-specific alterations were not accompanied by any significant change in circulating testosterone levels. We therefore conclude that 1) DES is much more potent that E2 as a neonatal endocrine disrupter in the male hamster, and 2) the DES-specific lesions in the adult male reproductive tract may represent a permanently altered androgen responsiveness in the affected target tissues.

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