Effect of sodium taurocholate on amiloride-inhibitable sodium uptake and on intracellular pH of isolated rat hepatocytes

Evidence is accumulating that bile salts affect cellular mechanisms for the transport of inorganic electrolytes. We investigated the effect of amiloride on ²²Na⁺ uptake rates in the presence and absence of sodium taurocholate (NaTC) and the effect of NaTC on intracellular pH (pHI) in isolated rat hepatocytes. Initial ²²Na⁺ uptake rates (nanomoles per milligram of protein per minute) were significantly suppressed by amiloride (0.6 mmol/L), although the effect was small. NaTC significantly increased ²²Na⁺ uptake rates. The amiloride-sensitive portion of ²²Na⁺uptake was significantly increased in the presence of NaTC (0.36 ± 0.07 SEM nmol/mg protein/min vs. 0.20 ± 0.07 nmol/mg protein/min, P < 0.02). The pHI was estimated by using the pH probes carbon 14-labeled 5,5′-dimethyloxazolidinedione and acridine orange. NaTC caused intracellular alkalinization. Amiloride caused intracellular acidification, and the reduction of pHI by amiloride was enhanced in the presence of NaTC, although this enhancement is difficult to interpret because of the large effects of amiloride on pHI relative to those of NaTC. Our results indicate that NaTC affects sodium uptake by isolated hepatocytes probably by stimulating the Na⁺-H⁺ antiport.