BETA-ADRENOCEPTORS OF HUMAN RED BLOOD-CELLS, DETERMINATION OF THEIR SUBTYPES

The characteristics of .beta.-adrenergic receptors of human erythrocyte membrane were investigated using (-)125iodocyanopindol as a radioligand. Inhibition of (-)125iodocyanopindolol specific binding was checked using either atenolol and metoprolol as .beta.1-selective antagonists or ICI 118551 [erythro-DL-1-(7-methylindcin-4-yloxy)-3-isopropylamino-butan-2-ol] and IPS 339 [(tert-butyl-amino-3-ol-2-propyl)oximino-9 fluorene] as .beta.2-selective antagonists. The results showed nonlinear Hofstee''s plots suggesting that both .beta.1- and .beta.2-adrenergic receptor are present. Analysis of data yielded a .beta.1/.beta.2 adrenergic receptor ratio of approximately 33/67. The .beta.2-subtype is evidently predominant on human erythrocyte membranes.