Effects of pH on basolateral tetraethylammonium transport in snake renal proximal tubules

Previous work on snake renal proximal tubules suggested that pH might influence tetraethylammonium (TEA) transport across the basolateral membrane. To examine this more directly, we determined the effects of altering either extracellular pH (pH(o)) or intracellular pH (pH(i)) on TEA uptake and efflux across the basolateral membrane of isolated snake renal proximal tubules. We found no evidence for trans-stimulation of either TEA uptake or efflux by H⁺. Therefore, there was no evidence for a TEA/H⁺ exchanger. However, we found evidence for trans-inhibition of both TEA uptake and efflux as well as for cis-inhibition of TEA uptake by increasing H⁺ concentration. H⁺ concentration appeared to have some type of direct effect on basolateral transport independent of any effect on membrane potential. Moreover, there appeared to be an optimal intracellular H⁺ concentration for entry of TEA into the cells that corresponded to the one found at the physiological pH(i) of 7.1. There also appeared to be an optimal extracellular H⁺ concentration for efflux of TEA from the cells that corresponded to the one found at the physiological pH(o) of 7.4. The mechanism involved in this relationship is unknown, but the data support a concept derived from previous studies that TEA transport across the basolateral membrane is asymmetric.