Beta adrenoceptors of human red blood cells, determination of their subtypes

The characteristics of beta adrenergic receptors of human erythrocyte membranes were investigated using (-)125iodocyanopindolol as a radioligand. Inhibition of (-)125iodocyanopindolol specific binding was checked using either atenolol and metoprolol as beta 1 selective antagonists or ICI 118551 and IPS 339 as beta 2 selective antagonists. The results showed non linear Hofstee's plots suggesting that both beta 1 and beta 2 adrenergic receptors are present. Analysis of the data yielded a beta 1/beta 2 adrenergic receptor ratio of approximately 33/67. Thus it is concluded that beta 2 subtype is predominant on human erythrocyte membranes.