Masutomi, N; Shibutani, M; Takagi, H; Uneyama, C; Takahashi, N; Arimura, T; Hirose, M
We have already evaluated the effects of candidates for endocrine disrupting chemicals (EDCs), genistein, diisononylphthalate, 4-nonylphenol, methoxychlor (MXC), bisphenol A and tamoxifen, on rat offspring following transplacental and lactational exposure during gestational day 15 to postnatal day 10. Among them, only MXC, at maternal dose of 1200 ppm in diet, affected endocrine/reproductive systems of offspring, such as enhancement of female puberty, delay in male puberty, and histopathological lesions in female reproductive organs. In this study, changes in ratio of LH, FSH or PRL-immunoreactive cells in anterior pituitary was assessed by immunohistochemistry using materials obtained in above studies. Pituitaries from rat offspring at 3 or 11 week of age, which were perinatally exposed to each chemical, were subjected to immunohistochemistry using rabbit antiserum raised against rat LH, FSH, or PRL (gifts from Dr. Parlow in NHPP/NIDDK, U.S.). The percentage of positively stained cells was evaluated for each hormone. Animals exposed to ethinylestradiol (EE) at 0.5 ppm were used as positive controls. At week 3, MXC decreased LH, FSH, and PRL-positive cells in males, and LH-positive cells in females at 1200 ppm. At week 11, MXC increased PRL-positive cells in females at 240 and 1200 ppm, and FSH-positive cells in females at 1200 ppm. EE increased PRL-positive cells in females at week 3, but showed no effects in both sexes at week 11. Other EDCs had no effects on any hormone-immunoreactivity at both weeks. The results obtained for MXC may suggest that the measurement of pituitary hormone-immunoreactive cells would be a sensitive tool to estimate the effects of endocrine disruption during postnatal period. The different outcomes between MXC and EE exposure suggest that the mode of action on the hypothalamus and/or pituitary differ depending on the strength and/or difference of hormonal activity between chemicals.
