Extracellular adenosine modulates a volume-sensitive-like chloride conductance in immortalized rabbit DC1 cells

Abstract

Cl−currents induced by cell swelling were characterized in an immortalized cell line (DC1) derived from rabbit distal bright convoluted tubule by the whole cell patch-clamp techniques and by125I− efflux experiments. Exposure of cells to a hypotonic shock induced outwardly rectifying Cl−currents that could be blocked by 0.1 mM 5-nitro-2-(3-phenylpropyl-amino)benzoic acid, 1 mM DIDS, and by 1 mM diphenylamine-2-carboxylate. 125I− efflux experiments showed that exposure of the monolayer to a hypotonic medium increased 125I− loss. Preincubation of cells with LaCl3 or GdCl3 prevented the development of the response. The addition of 10 μM adenosine to the bath medium activated outwardly rectifying whole cell currents similar to those recorded after hypotonic shock. This conductance was inhibited by the A1-receptor antagonist 8-cyclopentyl-1,3-diproxylxanthine (DPCPX), LaCl3, or GdCl3 and was activated by GTPγS. The selective A1-receptor agonist N 6-cyclopentyladenosine (CPA) mimicked the effect of hypotonicity on 125I− efflux. The CPA-induced increase of 125I− efflux was inhibited by DPCPX and external application of LaCl3 or GdCl3. Adenosine also enhanced Mn2+ influx across the apical membrane. Overall, the data show that DC1 cells possess swelling- and adenosine-activated Cl− conductances that share identical characteristics. The activation of both conductances involved Ca2+ entry into the cell, probably via mechanosensitive Ca2+ channels. The effects of adenosine are mediated via A1 receptors that could mediate the purinergic regulation of the volume-sensitive Cl−conductance.