Luteal Enzymes of the Luteinizing Hormone and β-Adrenergic Signal Transduction Pathways in Hypophysectomized Rabbits do not Require Pituitary Hormone Support1

Abstract

Experiments were conducted to determine whether continuous pituitary hormone support is required for expression of the LH and beta-adrenergic cAMP signal transduction pathways in rabbit CL during pseudopregnancy. Parameters of the LH and catecholamine cAMP signal transduction pathways in CL of estrogen-treated hypophysectomized rabbits were compared to those of pituitary-intact rabbits. Results showed that each of the parameters of the LH and beta-adrenergic cAMP signal transduction pathways was retained in CL taken from estrogen-treated pseudopregnant rabbits that had been hypophysectomized for as long as 13 days at levels not significantly different from those of estrogen-treated pituitary-intact rabbits. These included luteal basal, and LH-, epinephrine-, and fluoride-stimulated adenylyl cyclase activities; total luteal cAMP levels; the number and affinity of cAMP-dependent protein kinase regulatory subunit cAMP binding sites; binding activity of the type I and type II regulatory subunits; and the amount of catalytic subunit protein of cAMP-dependent protein kinase. We conclude that expression of the proteins of the cAMP signal pathway for LH and beta-adrenergic hormones in CL of estrogen-treated rabbits does not require pituitary hormone support.