Control of the proestrus surge of prolactin and luteinizing hormone secretion by estrogens in the rat.

An antiserum to estradiol was used to examine the role of estrogens secreted at diestrus in stimulating the proestrus surges of prolactin and luteinizing hormone (LH) secretion in the rat. Plasma prolactin and LH concentrations were measured by radioimmunoassay in blood samples obtained at 1–2 hr intervals on the day of proestrus in 4-day cyclic rats bearing aortic catheters. In control animals, proestrus prolactin values increased above baseline first at 1300 hr, were maximal between 1500–2000 hr, and returned to near baseline titers at 0100 hr on estrus. Proestrus LH concentrations were elevated first at 1500 hr, peaked at 1700–1800 hr, and fell to baseline values at 2300 hr. Estradiol antiserum administered at 1000 hr on proestrus did not affect the proestrus surge of prolactin and LH secretion or the incidence of vaginal cornification (100% vs. 94% in controls) and ovulation (88% vs. 71% in controls). On the other hand, estradiol∧ antiserum administered at 1000 hr on the day prior to proestrus (diestr...