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ADP‐ and epinephrine‐elicited release of [ 3 H]guanylylimododiphosphate from platelet membranes
Author(s) -
Motulsky Harvey J.,
Insel Paul A.
Publication year - 1983
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(83)80008-8
Subject(s) - epinephrine , platelet , membrane , chemistry , pharmacology , medicine , endocrinology , biochemistry
Epinephrine‐promoted release of [ 3 H]guanylylimidodiphosphate ([ 3 H]Gpp(NH)p) from human platelet membranes has been used to probe the interactions between alpha 2 ‐adrenergic recpetors and N i , the guanine nucleotide binding protein that couples those receptors to an inhibition of adenylate cyclase activity. We show here that ADP, which also acts through specific platelet receptors to inhibit adenylate cyclase activity, also promotes the release of [ 3 H]Gpp(NH). The amount of [ 3 H]Gpp(NH)‐release elicited by epinephrine and by ADP together is equal to the sum of the amounts released by the two agents acting individually. Furthermore the maximal amounts of [ 3 H]Gpp(NH)‐release elicited by each of the two agents approximates the numbers of receptors for ADP and epinephrine present in the platelet membranes. These results suggest that the two receptor types interact with distinct portions of the pool of N i molecules and that each receptor initiates guanine‐nucleotide exchange on a single molecule of N i .