Diabetes, Vol 30, Issue 2 172-174, Copyright © 1981 by American Diabetes Association

ARTICLES

Preponderance of beta-adrenergic binding sites in pancreatic islet cells of the rat

B Cherksey, N Altszuler and J Zadunaisky

Although the alpha- and beta-adrenergic receptors have opposing effects on insulin secretion, the inhibitory influence of alpha-receptors appears to predominate. To determine if this was due to differences in number and affinity of receptors, isolated rat pancreatic islet cells were incubated with [3H]-dihydroalprenolol and [3H]-dihydroergocryptine as ligands for beta- and alpha-adrenergic binding sites. It was found that the number of beta-adrenergic binding sites was 143 fmol/mg islet protein with a Kd = 0.57 nM. The number of alpha-adrenergic binding sites was 53 fmol/mg protein with a Kd = 0.26 nM. Thus, there are 2.7 times as many beta-adrenergic binding sites as alpha-binding sites, and neither binding site number nor affinity is responsible for the predominant influence of the alpha-adrenergic receptors.
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