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

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 by I-125(-) efflux experiments. Expo sure of cells to a hypotonic shock induced outwardly rectifying Cl- current s that could be blocked by 0.1 mM 5-nitro-2-(3-phenylpropyl-amino)benzoic a cid, 1 mM DIDS, and by 1 mM diphenylamine-2-carboxylate. I-125(-) efflux ex periments showed that exposure of the monolayer to a hypotonic medium incre ased I-125(-) loss. Preincubation of cells with LaCl3 or GdCl3 prevented th e development of the response. The addition of 10 mM adenosine to the bath medium activated outwardly rectifying whole cell currents similar to those recorded after hypotonic shock. This conductance was inhibited by the A(1)- receptor antagonist 8-cyclopentyl-1,3-diproxylxanthine (DPCPX), LaCl3, or G dCl3 and was activated by GTP gammaS. The selective A(1)-receptor agonist N -6-cyclopentyladenosine (CPA) mimicked the effect of hypotonicity on I-125( -) efflux. The CPA-induced increase of I-125(-) efflux was inhibited by DPC PX and external application of LaCl3 or GdCl3. Adenosine also enhanced Mn2 influx across the apical membrane. Overall, the data show that DC1 cells p ossess swelling- and adenosine-activated Cl- conductances that share identi cal characteristics. The activation of both conductances involved Ca2+ entr y into the cell, probably via mechanosensitive Ca2+ channels. The effects o f adenosine are mediated via A(1) receptors that could mediate the purinerg ic regulation of the volume-sensitive Cl- conductance.