PROSTAGLANDIN E-2 INCREASES 7-PS CL- CHANNEL DENSITY IN THE APICAL MEMBRANE OF A6 DISTAL NEPHRON CELLS

In A6 distal nephron cells, short-circuit current (I-sc) was increased by basolateral exposure to prostaglandin E-2 (PGE(2); peak response a t 1 mu M). The effect was only partially abolished by either apical am iloride, an Na+ channel blocker, or 5-nitro-2-(3-phenylpropylamino)ben zoic acid (NPPB), a Cl- channel blocker. In apical cell-attached patch es, we observed a 7-pS Cl- channel with a linear current-voltage relat ionship, a reversal potential near resting membrane potential, and ope n probability >0.5. The channel was blocked by diphenylamine-2-carboxy late, glibenclamide, and NPPB but not by 4,4'-diisothiocyanostilbene-2 ,2'-disulfonic acid. The frequency of observed Cl- channel activity in creased 7-fold with 10-min exposure to PGE(2) and 3.7-fold with longer (10-50 min) exposure to PGE(2). The PGE(2)-induced increase in Cl- ch annel activity was due primarily to an increase in the number of funct ional channels. The following conclusions were made: 1) activation of apical, 7-pS Cl- channels in A6 cells accounts for the PGE(2)-induced increase in the amiloride-insensitive I-sc, and 2) 7-pS Cl- channel ac tivation was mediated via an increase in channel density without subst antial effects on channel kinetics.