AJP - Renal Physiology, Vol 262, Issue 5 784-F792, Copyright © 1992 by American Physiological Society
pH dependence of the action of arginine vasopressin in renal collecting tubule
S. Ishikawa, K. Okada and T. Saito
Department of Medicine, Jichi Medical School, Tochigi, Japan.
We determined whether extracellular pH (pHe) and intracellular pH (pHi)
modulate the cellular actions of arginine vasopressin (AVP) in rat renal
papillary collecting tubule cells in culture. AVP significantly increased
cellular adenosine 3',5'-cyclic monophosphate (cAMP) production and
cellular free calcium concentration ([Ca2+]i). pHe ranging from 6.8 to 8.0
distributed the pHi between 6.94 and 7.27. The acidified pHe reduced the
AVP- and forskolin-induced cAMP production, the AVP-mobilized [Ca2+]i, and
[3H]AVP receptor binding, and the alkalinized pHe enhanced the AVP- and
forskolin-produced cAMP. Intracellular acidification occurred under three
different conditions as follows: using carbonyl
cyanide-m-chlorophenylhydrazone (CCCP), acetate buffer, and bicarbonate
buffer with a reduced concentration of bicarbonate. Intracellular
acidification significantly diminished both the AVP- and forskolin-induced
increases in cAMP production and the AVP-mobilized [Ca2+]i but did not
alter [3H]AVP receptor binding. Intracellular alkalinization by NH4Cl or
chloride-free bicarbonate buffer, in contrast, augmented them. These
results indicate that alterations in pHi modulate the cellular action of
AVP to produce cAMP and mobilize [Ca2+]i in renal papillary collecting
tubule cells. Also, reduced receptor binding of AVP is involved in the
mechanism of the effects of low pHe.
