Plasma Prolactin,Growth Hormone,Luteinizing Hormone and Glucocorticoids After Prostaglandin F 2α in Heifers 1

Abstract

Summary

Blood plasma PRL, GH and glucocorticoids in heifers increased severalfold within 5-15 min after im injections of 15, 30, or 60 mg PGF_2α or after a single 5 mg iv injection of PGF_2α. Plasma LH increased at least twofold over basal estimates but not until 1.5-6 hr after im PGF_2α. Constant iv infusion of PGF_2α at the rate of 0.5 mg/min for 30 min produced greater plasma concentrations of PRL, GH, glucocorticoids and LH than those found after im injections. Plasma glucose increased 59-67% above pretreatment values between 30 and 60 min after iv administration of PGF_2α. Plasma insulin increased more than twofold over basal estimates at 45 min after PGF_2α administration, but these increases only approached significance (P ≃ 0.10). Free fatty acids did not change significantly (P > 0.05) after PGF_2α administration. While exogenous PGF_2α administration causes marked increases in several plasma hormones and glucose, the mechanism of action is unclear.