BETA-ADRENERGIC INHIBITION OF NA-K-CL COTRANSPORT IN LYMPHOCYTES

Lymphocytes contain a homogeneous population Of beta2-adrenoceptors. However, their physiological role in the regulation of lymphocyte function, especially early in the activation/proliferation process, remains unclear. To study the role of beta-adrenergic activation on the regulation of membrane transport, we examined Rb-86 uptake in the Jurkat human lymphoma cell line. Rb-86 uptake was predominantly accounted for by bumetanide-sensitive uptake (74 +/- 2% total 86 Rb uptake) and ouabain-sensitive uptake (20 +/- 2%). Bumetanide potently inhibited Rb-86 uptake (50% inhibitory concentration + 210 +/- 40 nM), and bumetanide-sensitive uptake was dependent on extracellular sodium and chloride, consistent with uptake via Na-K-Cl cotransport. The beta-adrenergic agonist isoproterenol (10 muM) mediated a 50 +/- 11% reduction in bumetanide-sensitive uptake without a significant alteration in ouabain-sensitive uptake. The effect of isoproterenol was potent (50% effective concentration = 4.42 +/- 1.70 nM), stereoselective, and was inhibited by the beta-adrenergic antagonist nadolol. The effect of isoproterenol was mimicked by permeant adenosine 3',5'-cyclic monophosphate analogues but not by pindolol. These data indicate that beta-adrenoceptor activation decreases Rb-86 uptake in lymphocytes via inhibition of Na-K-Cl cotransport. Modulation of this transporter could be one mechanism by which beta-adrenergic agonists regulate lymphocyte function.