EVIDENCE OF THE EXISTENCE OF ALPHA(1B)-ADRENOCEPTORS ON HEPATOCYTES OF DOMESTIC-FOWL (GALLUS-DOMESTICUS)

In liver cell membranes of laying hens alpha(1)-adrenergic receptors w ere characterized using H-3-prazosin. Specific binding was saturable a nd indicative of a single class of high-affinity binding sites with a K-D of 0.40 +/- 16 nM and a B-max of 390 +/- 38 fmol/mg membrane prote in. Preincubation of membranes with chlorethylclonidine significantly diminished the binding of H-3-prazosin (B-max = 99 +/- 14 fmol/mg memb rane protein). Furthermore, competition experiments revealed a rank or der of prazosin much greater than phentolamine = oxymetazoline much gr eater than WB 4101, with K-i values of 0.71 +/- 0.62, 20 +/- 6, 32 +/- 13, and 119 +/- 18 nM, respectively. These results suggest the existe nce of alpha(1B)-adrenergic receptors in hen liver cell membranes.