ADRENERGIC RESPONSES OF R-RIDIBUNDA RED-CELLS

We studied the effects of beta-adrenergic stimulation on the formation of adenosine 3',5'-cyclic monophosphate (cAMP) and on the cell volume in Rana ridibunda red blood cells under O-2 (high oxygen atmosphere) and under N-2 (hypoxia) gases. Adrenergic stimulation caused the accum ulation of cAMP and the swelling of R. ridibunda erythrocytes. 10(-5) M adrenaline and 10(-5) M isoproterenol seem to be the more efficient concentration in causing greater cell swelling. The amount of cAMP req uired for adrenergic swelling was minimal; swelling was observed at cA MP concentrations higher than 20 nM. Maximal swelling was seen when th e cellular cAMP concentration reached 40 nM at high oxygen atmosphere. Isoproterenol caused a greater increase in water content than adrenal ine. At hypoxic conditions the water content and cAMP concentrations o btained after stimulation with adrenaline and isoproterenol were great er than at high oxygen atmosphere. Since the adrenergic response seems to be blocked both by prazosin and propranolole the adrenoreceptors o f R. ridibunda red cells may be classified as alpha(1)- and beta-recep tors. The enhancement of cAMP and cell swelling may be either due to a n increase in the number of adrenoreceptors, or to increased responsiv eness of the erythrocyte Na+-H+ antiporter to catecholamines during hy poxia. These responses are believed to enhance blood oxygen transport during periods of increased oxygen demands. (C) 1996 Wiley-Liss, Inc.