Apparently normal oestrogen receptor system in ovariectomized ewes with impaired response to oestrogen after prolonged grazing on oestrogenic pasture.

Functional abnormalities have been observed previously in the oestrogen-responsive tissues of ovariectomized ewes with permanent infertility resulting from prolonged exposure to oestrogenic pastures. In the present study, such ewes had higher rates of protein and glycoprotein synthesis in the cervix and uterus than control ewes, but the number of oestradiol-17 beta receptors in the nucleus was similar in each group. After treatment with oestradiol-17 beta, the increase in synthesis of protein and glycoprotein in the uterus and cervix was less in clover-affected ewes, but the amount of oestradiol-17 beta-receptor complex in the nucleus of uterine cells 6 h after ewes were injected with oestradiol-17 beta was similar in clover-affected and control ewes. The rate of replenishment of oestradiol-17 beta receptors in the cytoplasm at 24 and 48 h after oestradiol-17 beta injection was also similar in both groups. The abnormal function seen in the genital tract of clover-affected ewes could not, therefore, be shown to depend on changes in oestradiol-17 beta receptors.