Binding of 125I-iodohydroxybenzylpindolol to cerebral membranes: association with 5-hydroxytryptamine recognition sites as well as beta-adrenoceptors.
The binding characteristics of the radio-iodinated beta-adrenoceptor antagonist ligand 125I-iodohydroxybenzylpindolol (125I-IHYP) have been compared in membrane preparations derived from three different sources in a single mammalian species. In membrane preparations derived from rat lung and erythrocytes, 125I-IHYP binds solely to beta-adrenoceptors as defined by the stereoselectivity of the isomers of propranolol and the affinity of isoprenaline. However, in membranes prepared from rat cerebral cortex, although some 30% of 125I-HYP binding is to beta-adrenoceptors, a large proportion of the remainder is to sites that exhibit characteristics for 5-hydroxytryptamine (5HT) recognition. Thus, binding assays for 125I-IHYP in cerebral cortical membranes performed in the presence of 30 microM (-)-isoprenaline (to eliminate the binding of the ligand to beta-adrenoceptors) show that isomers of propranolol still maintain a degree of stereoselectivity at these sites. Also, 5HT and its congeners exhibit binding activity similar to that seen at 5HT receptors identified by 3H-5HT.
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D004910:Erythrocyte Membrane / Q000378:metabolism; D007457:Iodine Radioisotopes; D007545:Isoproterenol / Q000494:pharmacology; D008168:Lung / Q000378:metabolism; D008297:Male; D010646:Phentolamine / Q000494:pharmacology; D010869:Pindolol / Q000031:analogs & derivatives* / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D011985:Receptors, Serotonin / Q000378:metabolism*
D007457:Iodine Radioisotopes; D011943:Receptors, Adrenergic, beta; D011985:Receptors, Serotonin; C011878:iodohydroxybenzylpindolol; D010869:Pindolol; D007545:Isoproterenol; D010646:Phentolamine