Role for epithelial Na1 channels and putative Na1/H1 exchangers in salt taste transduction in rats

Lundy, Robert F., Jr., David W. Pittman, and Robert J. Contreras. Role for epithelial Na1 channels and putative Na1/H1 exchangers in salt taste transduction in rats. Am. J. Physiol. 273 (Regulatory Integrative Comp. Physiol. 42): R1923–R1931, 1997.—The effects of the epithelial Na1 channel antagonists amiloride and benzamil and the Na1/H1 exchange antagonist 5-(N,N-dimethyl)-amiloride (DMA)-Cl on the integrated responses of the chorda tympani nerve to 30, 75, 150, 300, and 500 mM concentrations of NaCl, KCl, and NH4Cl were assessed in male Sprague-Dawley rats. Based on evidence from other systems, 1 and 25 μM amiloride and benzamil were chosen to selectively inhibit epithelial Na1 channels and 1 μM DMA was chosen to selectively inhibit Na1/H1 exchange. When added to stimulating salt solutions, amiloride, benzamil, and DMA were each effective in inhibiting responses to all three salts. The degree of inhibition varied with drug, salt, and salt concentration, but not drug dose. Amiloride suppressed NaCl responses to a greater degree than KCl and NH4Cl responses, whereas DMA suppressed NH4Cl responses to a greater degree than NaCl and KCl responses. In all but one case (25 μM amiloride added to KCl), drug suppression of taste nerve responses decreased with an increase in salt concentration. The present results suggest that 1) epithelial Na1 channels in rat taste receptor cells may play a role in KCl and NH4Cl taste transduction; 2) a Na1/H1 exchange protein may be present in taste receptor cells, representing a putative component, in addition to epithelial Na1 channels, in salt taste transduction; and 3) salt taste detection and transduction may depend on the utilization of a combination of common and distinct transcellular pathways.