Karniski L P
Department of Internal Medicine, University of Iowa, Iowa City 52242.
J Membr Biol. 1989 Nov;112(1):59-66. doi: 10.1007/BF01871164.
The effect of the sulfhydryl reagent parachloromercuribenzoic acid (PCMB) on chloride transport was examined in rabbit renal brush-border membrane vesicles (BBMV). PCMB had no effect on the chloride conductive pathway. In the presence of an inside-alkaline pH gradient and a K-/valinomycin voltage clamp, the addition of PCMB stimulated 36Cl uptake and induced a threefold overshoot above the equilibrium value, indicating Cl/OH exchange. The effect of PCMB was reversed by dithiothreitol. Cl/OH exchange was not observed in the absence of PCMB. PCMB-activated Cl/OH exchange persisted even when the membrane potential was made inside-negative relative to the controls, thus, demonstrating that PCMB's effect on 36Cl uptake under pH-gradient conditions is not mediated by parallel Cl- and H+ conductive pathways. PCMB-activated Cl/OH exchange was inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) with IC50 values of 290 and 80 microM, respectively. These results demonstrate that modification of sulfhydryl groups by PCMB activates Cl/OH exchange in BBMV.
