AJP - Renal Physiology, Vol 251, Issue 5 897-F903, Copyright © 1986 by American Physiological Society
Fluctuations in intracellular pH associated with vasopressin stimulation
A. S. Brem, M. Pacholski and R. G. Lawler
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)
