Abstract
A high affinity, chemically reactive cyanopindolol derivative, N 8-bromoacetyl-N 1-3′-(2-cyano-4-indolyloxy)-2′-hydroxypropyl-[Z]-1,8-diamino-p-menthane (Br-CYP) was synthesized and its interaction with β-adrenoceptors characterized. Studies with rat heart, lung, brain, and red blood cell membranes indicated that the compound displaced 3H-dihydroalprenolol ( 3H-DHA) from β-adrenoceptors with IC 50 values in the nanomolar range. The concentration of functional β-adrenoceptors in membranes was markedly reduced when membranes were preincubated with Br-CYP and then extensively washed prior to assay. (±)Alprenolol and (-)isoproterenol, not (+) isoproterenol, when included in the preincubation prevented this reduction in binding sites by Br-CYP. Br-CYP was active in vivo when injected intraperitoneally into rats. A dose of 10 μg/kg reduced the concentration of binding sites in membranes from heart by 30%, lung by 36%, and RBC by 70%, but did not affect sites on brain membranes 16 hours after injection. Higher doses blocked virtually all the 3H-DHA binding sites in the peripheral organs studied. Br-CYP reduced the concentration of β-adrenoceptors in membranes from these same tissues (but not brain tissue) as long as two weeks after injection with recovery of binding occurring more rapidly in heart tissue than lung and red blood cells. These results suggest that Br-CYP may be a useful compound for in vivo studies of the biochemistry and pharmacology of β-adrenergic systems.
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