[The effect of sodium and ouabain on the activation of beta 2-adrenoreceptor-dependent adenylate cyclase in human lymphocytes].

Sodium inhibitory effect on adenylate cyclase activity of human mononuclear lymphocytes was investigated. Adenylate cyclase sensitivity to sodium inhibition was different upon cyclase stimulation with 1-isoproterenol, Gpp(NH)p and NaF. Sodium half-maximum inhibitory doze (ID50) was the smallest for 1-isoproterenol-stimulated adenylate cyclase activity (-40 mM). Cholera toxin did not exert influence on the inhibition of adenylate cyclase by sodium. Ouabain (10-100 microM) increased ID50 by 1.5 fold only for 1-isoproterenol-stimulated cyclase. It was observed that ID50 decreased after a short-term (15 min) 1-isoproterenol activation of intact lymphocytes. It is possible that the smallest sodium ID50 for 1-isoproterenol-stimulated adenylate cyclase is conditioned by sodium interaction with carboxylate residue of aspartate-79 from the cytoplasmic compartment of beta 2-adrenergic receptor (Horstman et al., 1990).