title: Preponderance of beta-adrenergic binding sites in pancreatic islet cells of the rat.
abstract: 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.
mesh_terms: D000818:Animals; D001665:Binding Sites; D004082:Dihydroalprenolol / Q000378:metabolism; D004088:Dihydroergotoxine / Q000378:metabolism; D007515:Islets of Langerhans / Q000032:analysis* / Q000378:metabolism; D008297:Male; D009924:Organ Culture Techniques; D011869:Radioligand Assay; D051381:Rats; D011941:Receptors, Adrenergic / Q000032:analysis*; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000032:analysis* / Q000378:metabolism
chemical_list: D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D004088:Dihydroergotoxine; D004082:Dihydroalprenolol