Soichiro Sekiguchi

Effects of in utero exposure to 2,2′,4,4′,5,5′‐hexachlorobiphenyl (PCB 153) on somatic growth and endocrine status in rat offspring

ABSTRACT  Exposure to polychlorobiphenyl (PCB) mixtures at an early stage of development has been reported to affect endocrine glands; however, little is known about the precise toxicological properties of individual PCB. The present study was undertaken to determine whether prenatal exposure to 2,2′,4,4′,5,5′‐hexachlorobiphenyl (PCB 153), a di‐ortho‐substituted non‐coplanar congener, affects postnatal development in rat offspring. Pregnant Sprague‐Dawley rats (Crj: CD (SD) IGS) were given PCB 153 (0, 16, or 64 mg/kg/day) orally from gestational day (GD) 10 through GD 16, and developmental parameters in the male and female offspring were examined. We found no dose‐dependent changes in body weight, body length (nose–anus length), tail length, or the weights of kidneys, testes, ovaries and uterus in offspring at 1 or 3 weeks of age. Liver weights were increased in the PCB 153–treated groups, although we observed a significant difference only in males. Anogenital distance was unaffected in the PCB 153–treated groups. We observed a significant dose‐dependent decrease in the plasma concentrations of thyroxine and tri‐iodothyronine, whereas those of thyroid‐stimulating hormone were not significantly changed. In addition, there were no dose‐dependent changes in plasma concentrations of growth hormone and insulin‐like growth factor‐I in any dose group. These findings suggest that prenatal exposure to PCB 153 (GD 10–16, 16–64 mg/kg/day) may alter the thyroid status in rat offspring to some extent without affecting somatic growth or its related hormonal parameters.

Influence of 2-bromopropane on reproductive system--short-term administration of 2-bromopropane inhibits ovulation in F344 rats.

The present study was performed to investigate the toxic effects of 2-bromopropane (2BP) on the female reproductive system. Female F344 rats were administered 2BP (500 or 1000 mg/kg, i.p.) at intervals of 2 or 3 days for 15-17 days. The body weights were measured and estrous stages were observed throughout the experimental period. Ovulation, organ weights, ovarian histology, and blood biochemistry were investigated on the terminal day of the experiment. Uterine weights in rats treated with 2BP were significantly lower than those in control animals. Body, liver, kidney, and adrenal weights in 2BP-treated rats showed no significant differences from control values. 2BP treatment prolonged estrous cycles and decreased the number of ovulated ova in spontaneous ovulation. In addition, histological examinations showed that the preovulatory follicles in the ovary were altered markedly in 2BP groups. These results show that even in short-term treatment, 2BP injured the ovary, particularly the preovulatory follicles. It appears that these damages of the preovulatory follicles induced by 2BP reduced the numbers of spontaneously ovulated ova in female F344 rats.