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  • Title: Studies on isoproterenol stimulation of adenyl cyclase in membrane preparations from the bovine thyroid.
    Author: Marshall NJ, von Borcke S, Malan PG.
    Journal: Endocrinology; 1975 Jun; 96(6):1520-4. PubMed ID: 1126319.
    Abstract:
    Catecholamine stimulation of adenyl cyclase activity associated with bovine subcellular fractions enriched in plasma membranes is described. The relative potencies of isoproterenol (IPNA), epinephrine (E), and norepinephrine (NE) were 4.7:1.0:0.02, which is characteristic for a beta-adrenergic receptor system. Stimulation with IPNA (5 times 10- minus 6 M) was inhibited by propranolol. The inhibition was stereospecific for the L-isomer of propranolol and a concentration as low as 2 times 10- minus 8 M was required to effect 50% inhibition. Both these observations, and the competitive kinetics of inhibition which applied to the system, confirmed the classification of a beta-adrenergic receptor system. Phentolamine, an alpha-antagonist, also inhibited IPNA stimulation, although high doses (5 times 10- minus M) were required to cause total inhibition. Inhibition was also observed with quinidine (1 mM) and lignocaine (10- minus 2 M).
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