Biochemical properties of adenosine receptors in an enriched fraction of plasma membranes from canine ventricle
The binding of /sup 3/H-phenylisopropyladenosine to a sarcolemma-enriched fraction from canine ventricle was characterized at 37/sup 0/C using a vacuum filtration technique. /sup 3/H-phenylisopropyladenosine binding was rapid, reaching equilibrium within 10 min and was readily reversible, displaying a dissociation half-life of 1.7 min. Specific /sup 3/H-phenylisopropyladenosine binding to the cardiac membrane preparation was saturable with increasing free ligand concentrations and Scatchard analysis indicated a single class of binding sites having a B/sub max/ of 601 fmol/mg protein. The K/sub d/ of /sup 3/H-phenylisopropyladenosine for its binding site was 52-85 nM as determined independently from kinetic and equilibrium studies, respectively. Binding was stereospecific in that (-)phenylisopropyladenosine was 9-fold more potent than (+)phenylisopropyladenosine in competing for /sup 3/H-phenylisopropyladenosine binding sites. Although (-)phenylisopropyladenosine had no effect on basal adenylate cyclase activity in cardiac membranes, the nucleoside had a biphasic effect on isoproterenol-activated adenylate cyclase. A maximal 21.6 +/- 3.9% inhibition of isoproterenol-activated adenylate cyclase was observed at 1 ..mu..M (-)phenylisopropyladenosine while higher concentrations reversed the inhibitory effect.
- Research Organization:
- South Carolina Univ., Columbia (USA)
- OSTI ID:
- 6655331
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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