Relationship between pituitary nuclear oestrogen receptors and the release of LH, FSH and prolactin in the ewe.

Ovariectomized ewes were given a single injection (i.v.) of 100 micrograms oestradiol-17 beta. Nuclear oestrogen receptor values in the pituitary, as a function of total receptor concentrations, were 3.0 +/- 1.0% in controls, 56.0 +/- 5.4% at 1 h (P less than 0.001) and 6.5 +/- 2.1% at 6 h (P less than 0.05) after oestradiol injection. There was a fall in plasma LH values from 5.7 +/- 1.0 (preinjection) to 2.1 +/- 0.3 ng/ml (P less than 0.01) 4-6 h after oestradiol. At 13-21 h after injection plasma levels increased to 37 +/- 8 ng/ml (P less than 0.001). Plasma FSH levels declined from 840 +/- 18 to 506 +/- 48 ng/ml after 20-22 h (P less than 0.001). Plasma prolactin concentrations fell from 90 +/- 16 ng/ml before injection to 29 +/- 9 ng/ml at 1 h (P less than 0.05), and then rose to a maximum of nuclear compartmentalization of oestrogen receptors after a bolus injection of oestradiol was associated with the feedback effects of oestradiol on LH, FSH and prolactin release.