Inhibition of K conductance in descending vasa recta pericytes by ANG II.

We tested whether K+ channel inhibition accompanies ANG II-induced depolarization of descending vasa recta (DVR) pericytes. An increase in extracellular K+ concentration ([K+]o) from 5 to 100 mM depolarized resting pericytes but had no effect after prolonged (10 nM, 20 min) ANG II exposure. In contrast, reduction of extracellular Cl- concentration ([Cl-]o) from 154 to 34 mM had a minor effect on resting membrane potential but strongly depolarized pericytes treated with ANG II. The K+ channel blockers BaCl2 (0.1, 1 mM) and tetraethylammonium (TEA; 30 mM) depolarized resting pericytes but did not affect membrane potential of ANG II-treated pericytes. Pericyte whole cell currents were reduced by ANG II and nearly eliminated by combined ANG II exposure and the Cl- channel blocker niflumic acid (100 &mul;M). Augmentation of inward current induced by raising [K+]o from 5 to 50 mM was eliminated by preexposure to ANG II. TEA- and BaCl2-sensitive outward currents, generated by depolarizing pericytes from -80 to -40 mV, were eliminated by ANG II. We conclude that ANG II depolarizes DVR pericytes by a combination of Cl- channel activation and K+ channel inhibition. [ABSTRACT FROM AUTHOR]