Effect of bicarbonate and furosemide on chloride accumulation by the intestine of the freshwater turtle Mauremys caspica.

: The influence of HCO3- on Cl- absorption by the intestine of the freshwater turtle Mauremys caspica has been studied. Na+, K+ and Cl- intracellular concentrations together with transepithelial potential difference were measured. In HCO3--free medium, transepithelial potential difference was serosal positive. A reversal in the sign of the transepithelial potential difference was observed in HCO3- medium. A subsequent addition of 10(-3) M furosemide to HCO3- medium blocked, at least partially, this response. However, neither the presence of HCO3- nor addition of 10(-3) M furosemide to HCO3+ medium had any effect on Na+, K+ or Cl- intracellular concentrations. These results are discussed in relation to the presence of a Cl-/HCO3- exchange process.