Changes in the suppressive effects of recombinant inhibin A on FSH secretion in ram lambs during sexual maturation: Evidence for alterations in the clearance rate of inhibin

Abstract

We have investigated the effectiveness of human recombinant inhibin A (hr-inhibin A) to suppress the secretion of follicle-stimulating hormone (FSH) in ram lambs from 1 to 18 months of age. Seventeen rams (nine castrated, eight intact) were used. At 1, 3, 6, 9, 12 and 18 months of age the rams were given an i.v. injection of either vehicle or hr-inhibin A (0.64 μg/kg). Blood samples were taken over 24 h. Plasma concentrations of FSH were suppressed in castrated and intact rams following injection of hr- inhibin A with maximal suppression occurring 6 h after injection. Vehicle injection had no effect. At 12 months of age the suppression in FSH was most rapid in castrated rams and was maximal ..