Antidiuretic hormone decreases the intracellular pH in distal nephron epithelium (A6) by inhibiting Na+/H+ exchange

Abstract 1. 1. To clarify the effect of arginine vasotocin (AVT) on intracellular pH (pH i ) of A6 cells (an amphibian renal cell line), we measured pH i with a single-cell fluorescent imaging system in an HCO 3 − nominally-free medium. 2. 2. AVT (40mU/ml) significantly decreased pH i from 7.44 ± 0.11 to 7.19 ± 0.22 (mean ± SE) by inhibiting the Na + /H + exchanger. 3. 3. A membrane-permeable analogue of cAMP, dibutyryl cAMP (1mM), significantly decreased pH i from 7.40 ± 0.02 to 7.17 ± 0.02, a response similar to that of AVT. 4. 4. These data indicate that, in A6 cells, AVT suppresses the Na + /H + exchanger via a cAMP-dependent pathway and the Na + /H + exchanger maintains pH i under HCO 3 − -nominally-free conditions.