Effects of NH4Cl and dimethylamine on Cl- fluxes in resting and stimulated rat submandibular acinar cells.

Transmembrane movements of K+ and Cl- in salivary acinar cells are important in the formation of saliva, and may be affected by changes in intracellular pH (pHi). Exposure to NH4Cl increases pHi transiently, but NH4+ may have effects independent of pHi. To investigate how Cl- transport may be altered under these conditions, rat submandibular acini were exposed to NH4Cl, and transmembrane Cl- transport was studied with 36Cl-. NH4Cl increased intracellular Cl- in these cells. The initial phase of this increase was partially HCO(3-)-dependent and was inhibited by 1 mM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), while the sustained phase was inhibited by 0.1 mM bumetanide. NH4Cl also inhibited acetylcholine-induced Cl- efflux from tracer preloaded cells. Changes in pH did not always correlate in time or extent with those of Cl- transport. We conclude that 1) exposure to NH4Cl increases Cl-uptake primarily by a bumetanide-sensitive transport system that did not reach steady state during the experiment, 2) exposure to NH4Cl also stimulates Cl- uptake by a DIDS-sensitive mechanism, and 3) only the latter is pHi sensitive.