Effects of ammonium chloride on membrane currents of acinar cells dispersed from the rat parotid gland

Abstract

In acinar cells freshly dispersed from rat parotid glands, the effects of ammonium chloride (NH₄Cl) on membrane currents were studied using the whole-cell clamp method. When membrane currents were recorded with command pulses to 0 mV, applied at 2-s intervals from a holding potential of −70 mV, NH₄Cl (5–20 mM) transiently decreased outward currents and then slowly increased both outward and inward currents. After reaching a peak in about 40–50 s, both outward and inward currents gradually decreased in the presence of NH₄Cl and, on its wash-out, the currents returned to the control level. Butyrate (5–20 mM) had little effect on the resting membrane currents, but markedly inhibited the response to NH₄Cl. Tetraethylammonium (5 mM) strongly reduced both the resting and NH₄Cl-induced outward currents, whereas it slightly potentiated the NH₄Cl-induced inward current without affecting the membrane current at the holding potential. Without ATP in the patch pipettes, carbachol-induced membrane currents were relatively resistant to Ca²⁺ removal from the external medium, but NH₄Cl-induced currents were quickly abolished in the absence of Ca²⁺. We conclude that intracellular alkalinization with NH₄Cl increases Ca²⁺ influx and activates Ca²⁺-dependent outward K⁺ and inward Cl⁻ currents.