REGULATION OF NA+/H+ EXCHANGE BY DIADENOSINE POLYPHOSPHATES, ANGIOTENSIN-II, AND VASOPRESSIN IN RAT CORTICAL COLLECTING DUCT

In principal cells of rat cortical collecting ducts (CCD) cellular pH (pH(i)) is regulated by basolateral Na+/H+ exchange. The influence of various agonists on pH(i) and cellular Ca2+ activity ((Ca2+)(i)) in freshly isolated CCD cells was examined with BCECF and fura-2 fluorescence ratios. The recovery of pH(i) per minute (Delta pH/ min) after an acid load was 0.26 + 0.03 (N = 53) in control conditions and was increased by the diadenosine polyphosphates Ap(4)A, Ap(5)A, Ap(6)A, the phorbol ester phorbol 12-myristat 13-acetate (PMA) (each 5 mu mol/L) and angiotensin II (100 nmol/L) by 0.05 +/- 0.02 (N = 10), 0.11 +/- 0.05 (N = 13), 0.09 +/- 0.02 (N = 24), 0.10 +/- 0.03 (N = 7), and 0.09 +/- 0.03 (N = 8), respectively. Vasopressin (10 nmol/L) decreased Delta pH/min by 0.11 +/- 0.03 (N = 9); ATP and Ap(3)A (each 5 mu mol/L) had no significant effect. The increase in Delta pH/min with Ap(6)A was abolished in the presence of an inhibitor of protein kinase C, calphostin C (0.1 mu mol/l, N = 8). Fura-2 fluorescence ratio was not significantly changed with angiotensin II, Ap(3)A, or Ap(4)A but increased with vasopressin, ATP, Ap(5)A, and Ap(6)A by 0.08 +/- 0.02 (N = 13), 0.04 +/- 0.02 (N = 13), 0.03 +/- 0.01 (N = 14), and 0.03 +/- 0.01 (N = 10), respectively. These data indicate that Na+/H+ exchange in rat CCD is activated by the stimulation of a Ca2+-independent protein kinase C and inhibited by protein kinase A.