Fluctuations in intracellular pH associated with vasopressin stimulation.

Abstract

Intracellular pH (pHi) was estimated in paired hemibladders isolated from Dominican toads (Bufo marinus) by the tissue distribution of [14C]5,5'-dimethyl-2,4-oxazolidinedione and [3H]inulin. Tissues were incubated with isotopes for 30 min to correlate changes in pHi with the approximate time of peak vasopressin (VP)-induced water flow. At serosal pH 7.1 in the presence of an osmotic gradient, the intracellular hydrogen ion concentration [( H+]i) after 30 min of VP (20 mU/ml) stimulation was 8.29 +/- 0.23 X 10(-8) M (pHi 7.08) compared with 5.19 +/- 0.46 X 10(-8) M (pHi 7.28) in unstimulated paired controls (n = 5, P less than 0.001). The cyclic AMP (cAMP) analogue 8-(p-chlorophenylthio)-cAMP (10(-5) M) mimicked the VP effects. A similar change was observed at serosal bath pH 8.2, where [H+]i was 1.67 +/- 0.06 X 10(-8) M (pHi 7.78) with VP vs. 1.11 +/- 0.04 X 10(-8) M (pHi 7.95) in matched controls (n = 8, P less than 0.001). In all cases, the hydroosmotic response was associated with a significant decrease in inulin space. When the osmotic gradient was eliminated with Ringer solution or isotonic sorbitol in the mucosal bath, VP produced a smaller decrease in pHi (approximately 0.08 pH units) at both serosal pH. 31P-nuclear magnetic resonance spectra showed a similar downward trend in pHi with cell swelling. When vasopressin was removed from the bath, pHi and inulin space in stimulated hemibladders returned to pretreatment values within 30 min, and the tissues were again capable of a maximum hydroosmotic response if rechallenged with the hormone.(ABSTRACT TRUNCATED AT 250 WORDS)