Beta-adrenergic receptor concentration in corpora lutea of different ages obtained from pregnant mare serum gonadotropin-treated rats

Abstract

We have measured the beta-adrenergic receptor content in 1- to 10-day-old corpora lutea. Corpora lutea of defined ages were obtained by sc injection of 8 IU PMSG to 26-day-old rats, leading to ovulation and formation of corpora lutea in the early morning of day 29. Membrane fractions of isolated corpora lutea were incubated with various concentrations of the beta-adrenergic antagonist [125I]iodohydroxybenzylpindolol [125I]iodo-HYP, 12.5-2500 pM) for 60 min at 22 C. Alprenolol (10(-5) M) was used to determine nonspecific binding. Bound and free [125I]iodo-HYP was separated by filtration and washing on Whatman GF/C filters under vacuum. There was a 3-fold increase in beta-adrenergic receptor concentration during the first 2-3 days of corpus luteum formation, followed by a decline in the beta-adrenergic receptor content with luteal age. The rat luteal beta-adrenergic receptor seems to be of the beta 2-subtype as determined from adenylate cyclase stimulation as well as from displacement of [125I]iodo-HYP binding by various beta-adrenergic agonists.