Alteration of pituitary hormone-immunoreactive cell populations in rat offspring after maternal dietary exposure to endocrine-active chemicals.

We previously performed dose-response studies of genistein, diisononyl phthalate, 4-nonylphenol, methoxychlor (MXC), and bisphenol A to examine the impact of maternal dietary exposure from gestational day 15 to postnatal day 10 on the development of rat reproductive system in later life. Among the chemicals MXC alone showed typical estrogenic effects only at the maternally toxic 1200 ppm. The present study was performed to examine the sensitivity of immunohistochemical analysis of pituitary cells of offspring similarly exposed to each chemical for detection of endocrine-disrupting effects. For this purpose, ratios of pituitary cells expressing luteinizing hormone (LH), follicle stimulating hormone (FSH) and prolactin (PRL), were measured at 3 and 11 weeks of age. Ethinylestradiol (EE) at 0.5 ppm was used as a reference chemical. At week 3, decrease in the relative proportions of LH, FSH, and PRL cells in males and LH cells in females was evident with MXC at 1200 ppm. At week 11, increase was found for PRL cells from 240 ppm MXC, and FSH cells at 1200 ppm in females. On the other hand, EE increased the PRL cell percentage in females at week 3 but no effects were apparent at week 11. The other chemicals were without influence at either time point. The results suggest that the assessment of the pituitary cell populations might be a more sensitive approach to detect perinatal endocrine-disrupting effects than other methods. The difference in the pituitary effect between MXC and EE is discussed.