Long-term effects on reproductive parameters in female rats after translactational exposure to PCBs.

In an integrated series of experiments, we assessed effects of translactational exposure to Aroclor 1254 at three different ages: as young adults (2-4.5 months), as mature adults (5-8 months), and as older adults (8.5-13 months). Developing female rats were exposed postnatally to polychlorinated biphenyls (PCBs) via oral treatment of the dams on Days 1, 3, 5, 7, and 9 of lactation at the following doses: 8 micrograms/g (PCBI), 32 micrograms/g (PCBII), and 64 micrograms/g (PCBIII) in peanut oil. Normal controls (CI) and underfed nutritional controls (CII) received peanut oil. Puberty, both vaginal opening and first estrus, was delayed in PCBII and PCBIII offspring. PCB exposure at all doses had a pronounced and consistent effect on uterine response. In mature PCBII and PCBIII adults, uterine wet weights were reduced at all stages of the estrous cycle and in light-induced persistent vaginal estrus (PVE). PCBI offspring exhibited a decreased uterine weight in proestrus and in light-induced PVE. Exogenous estradiol-17 beta (0.2 microgram) given to ovariectomized offspring was less effective in causing a uterotrophic and vaginal response in all PCB-exposed offspring. Analysis of estrous cycles for 40 days at all ages indicated increases in diestrus. Fertility in young adults and mature adults was affected, with PCBIII young adults exhibiting less success with preimplantation stages, and PCBII and PCBIII mature adults showing an effect at pre- and/or postimplantation stages. As determined by patterns in estrous cycling and rate of development of PVE in 64 days of constant light, exposure to PCBs did not hasten reproductive aging at any of the ages examined. Instead, PCBIII young adults and PCBII and PCBIII older adults exhibited a delay in onset of light-induced PVE. This study demonstrates that translational exposure to a PCB mixture that has little notable effect on the dams, not only delays puberty in the female offspring, but also several months later results in decreased uterine response, impairment of fertility, and irregular cycle patterns. Reproductive aging, however, is not hastened, and even may be delayed. Many of these effects could be explained, in part, by interference with estrogen.

The use of Markov chains to detect subtle variation in reproductive cycling.

Certain reproductive parameters in animals are particularly sensitive endpoints in toxicological experiments. Measured changes in one of these endpoints, estrous cycling in the rat, can reflect aberration in the underlying hormonal environment or end organ response. This article proposes the use of Markov chains to measure subtle changes in estrous cycling not readily detectable by standard methods of analysis.

Effect of postnatal exposure to polychlorinated biphenyls on adult male reproductive function.

Polychlorinated biphenyls (PCBs) have been found widely distributed in the ecosystem, including human milk, yet there is limited information concerning the effect that PCB exposure during the postnatal period might have on subsequent reproductive capacity of adult male offspring. In this study, fertility and condition of reproductive organs were examined in male offspring of rats that received Aroclor 1254 orally (8, 32, or 64 mg/kg) on Days 1-3, 5, 7, and 9 of lactation. It was found that the experimental male offspring as adults were less successful in mating and reproducing when compared with control offspring. Virgin females mated with males exposed through suckling to the two higher doses of PCBs had a significantly lower proportion of ovulated eggs that implanted, a significantly lower number of live fetuses, and a significantly higher rate of resorption. At autopsy, although body weights were not significantly different, ventral prostate weights were significantly less in all treated male offspring; there were fewer alveoli and flattened epithelial cells in these glands as compared to controls. Seminal vesicle weights were significantly less in males exposed to the two higher doses of PCBs, while the testes were significantly larger. PCB-derived material remained in adipose tissue and liver at the time of autopsy. These data support the hypothesis that exposure of male offspring to PCBs during early postnatal development results in an hypoandrogenic condition that is detrimental to normal reproductive functioning in the adult.