Biochemical identification of the beta-adrenoceptor and evidence for the involvement of an adenosine 3',5'-monophosphate system in the beta-adrenergically induced release of alph-melanocyte-stimulating hormone in the intermediate lobe of the rat pituitary gland

Endocrinology
T CoteJ W Kebabian

Abstract

The beta-adrenoceptor in the intermediate lobe (IL) of the hypophysis of the rat is characterized on the basis of the following: 1) the ability of beta-adrenergic agonists to increase adenylate cyclase activity in homogenates of the IL, and 2) the ability of drugs active upon the beta-adrenoceptor to compete with [125I]hydroxybenzylpindolol, a radiolabeled beta-adrenergic antagonist, for high affinity (Kd = 232 pM) binding sites. The values of the affinity of the beta-adrenoceptor for drugs obtained in either assay system are in good agreement. The relative potency among agonists, L-isoproterenol greater than L-epinephrine greater than L-norepinephrine, suggests that the receptor is of the beta-2 subcategory. cAMP, derivatives of cAMP, and a phosphodiesterase inhibitor, theophylline, mimic the ability of l-isoproterenol to enhance the release of alpha MSH from dispersed cells of the rat IL. The present results are in accord with the possibility that occupancy by agonists of the beta-adrenoceptor of the IL enhances adenylate cyclase activity, resulting in an accumulation of cAMP which initiates the intracellular events that are ultimately expressed as an enhanced release of alpha MSH. Pharmacological data suggest that stimulatio...Continue Reading

Citations

Mar 1, 1988·Cell and Tissue Research·N BäckT Laatikainen
Mar 1, 1988·Cellular and Molecular Neurobiology·Y FurukiJ W Kebabian
Jul 30, 1982·European Journal of Pharmacology·W KnepelG Hertting
Jul 1, 1982·Molecular and Cellular Endocrinology·K P Ray, M Wallis
Nov 1, 1986·Brain Research Bulletin·S SchimchowitschG Pelletier
Jan 1, 1985·Journal of Ocular Pharmacology·T Yorio
Sep 1, 1987·Journal of Clinical Pathology·S Al-Damluji, L H Rees
May 1, 1987·Baillière's Clinical Endocrinology and Metabolism·R C Gaillard, S Al-Damluji
May 31, 1993·Annals of the New York Academy of Sciences·P LimoneG M Molinatti

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