Supra-additive stimulation of adenylate cyclase activity by prostaglandin E sub(2) and D-Ala super(2)-met-enkephalinamide in the guinea-pig superior cervical ganglion: Role of Mg super(2+) ions

Agonists modulation of Mg super(2+)-dependent adenylate cyclase activity has been studied in guinea-pig superior cervical ganglion crude membrane preparations. In the absence of receptors ligands, Mg super(2+) stimulates the enzyme in a concentration-dependent manner. In the presence of D-Ala super(...

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Published in:Neurochemical research 1989-01, Vol.14 (12), p.1181-1186
Main Authors: Borasio, P G, Biondi, C, Ferretti, ME, Fabbri, E, Pareschi, M C
Format: Article
Language:English
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Summary:Agonists modulation of Mg super(2+)-dependent adenylate cyclase activity has been studied in guinea-pig superior cervical ganglion crude membrane preparations. In the absence of receptors ligands, Mg super(2+) stimulates the enzyme in a concentration-dependent manner. In the presence of D-Ala super(2)-met-enkephalinamide only one component is present and the apparent affinity of the ganglionic adenylate cyclase system for the divalent cation as well as Vmax are inhibited. When the two drugs are tested in combination, not only the inhibitory effect of the opiate is overcome, but a large increase of the apparent affinities and Vmax values for both components in obtained, suggesting the involvement of the Mg super(2+)- regulated subunits of the adenylate cyclase system in the supra-additive stimulation mechanism of the enzyme.
ISSN:0364-3190