ACTIVE ALPHA2-ADRENOCEPTOR AND BETA-ADRENOCEPTOR IN LYMPHOCYTES FROM PATIENTS WITH CHRONIC LYMPHOCYTIC-LEUKEMIA

A single population of alpha2 adrenoceptors was characterized in intact B lymphocytes from patients with chronic lymphocytic leukemia (B-CLL) by binding and saturation studies with H-3 labelled yohimbine and by competition studies with alpha adrenergic antagonists. While the affinity of B-CLL alpha2 adrenoceptors was low (K(D): 9.81 nM-20.98 nM), each cell expressed a large number of receptors. No binding of the alpha1 adrenoceptor antagonist prazosin was observed and the binding properties of beta adrenergic receptors (assayed with H-3-labelled dihydroalprenolol), were similar to those described for normal lymphocytes. Reaction of B-CLL with the beta adrenergic agonist isoproterenol raised the levels of cAMP in 11/13 patients tested, and in 8 of these, incubation with the alpha2 adrenergic agonist clonidine prevented the effect and reduced the basal cAMP levels. The presence of active alpha2 adrenoceptors on B-CLL lymphocytes may be involved in the regulation of metabolic pathways that affect cell functions and favor neoplastic growth.