Adenosine inhibits the basolateral Cl ClC-K2/b channel in collecting duct intercalated cells.

Adenosine plays an important role in various aspects of kidney physiology, but the specific targets and mechanisms of actions are not completely understood. The collecting duct has the highest expression of adenosine receptors, particularly adenosine A receptors (ARs). Interstitial adenosine levels are greatly increased up to a micromolar range in response to dietary salt loading. We have previously shown that the basolateral membrane of principal cells has primarily K conductance mediated by K4.1/5.1 channels to mediate K recycling and to set up a favorable driving force for Na/K exchange (47). Intercalated cells express the Cl ClC-K2/b channel mediating transcellular Cl reabsorption. Using patch-clamp electrophysiology in freshly isolated mouse collecting ducts, we found that acute application of adenosine reversely inhibits ClC-K2/b open probability from 0.31 ± 0.04 to 0.17 ± 0.06 and to 0.10 ± 0.05 for 1 and 10 µM, respectively. In contrast, adenosine (10 µM) had no measureable effect on K4.1/5.1 channel activity in principal cells. The inhibitory effect of adenosine on ClC-K2/b was abolished in the presence of the AR blocker 8-cyclopentyl-1,3-dipropylxanthine (10 µM). Consistently, application of the AR agonist -cyclohexyladenosine (1 µM) recapitulated the inhibitory action of adenosine on ClC-K2/b open probability. The effects of adenosine signaling in the collecting duct were independent from its purinergic counterpartner, ATP, having no measurable actions on ClC-K2/b and K4.1/5.1. Overall, we demonstrated that adenosine selectively inhibits ClC-K2/b activity in intercalated cells by targeting ARs. We propose that inhibition of transcellular Cl reabsorption in the collecting duct by adenosine would aid in augmenting NaCl excretion during high salt intake.