Serum and Pituitary LH Concentrations in Ewes Infused with LH-RH/FSH-RH2

Abstract

Twenty anestrous ewes (mean body weight 68 kg) were assigned at random in a 2 × 2 factorial experiment. The ewes were continuously infused with synthetic LH-RH/FSH-RH or acidified saline for a period of 24 hours. Half of the ewes in each group were pretreated with a synthetic progestagen (flurogestone acetate) for 14 days prior to infusion. Serum and pituitary LH concentrations, serum estrogen concentration, stalk median eminence (SME) LH-releasing activity, and ovarian characteristics were studied. Infusion with LH-RH/FSH-RH at the rate of 2.3 µg/hr. induced a significant increase in serum LH concentrations, which peaked (23 to 30 ng/ml) at 3 hr. and decreased to pretreatment LH concentration (0.7 ng/ml) by 16 hours. There were no differences in peak serum LH concentrations or duration of LH response due to pretreatment with the synthetic progestagen. Infusion with LH-RH/FSH-RH lowered pituitary LH content and concentration but had no effect on serum estrogen levels, pituitary dry weight, stalk median eminence LH-releasing activity, ovarian weight, or ovarian follicular diameter. Copyright © 1974. American Society of Animal Science . Copyright 1974 by American Society of Animal Science.