AJP - Regulatory, Integrative and Comparative Physiology, Vol 267, Issue 1 107-R114, Copyright © 1994 by American Physiological Society
Na+ transport and pH in principal cells of frog skin: effect of antidiuretic hormone
V. Lyall, T. S. Belcher, J. H. Miller and T. U. Biber
Department of Physiology, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298-0551.
Intracellular pH (pHi), apical membrane potential (Va), and fractional
apical membrane resistance (FRa) were measured in principal cells of
isolated frog skin (Rana pipiens) with double-barreled microelectrodes
under short-circuit conditions. Basolateral exposure to 10 mU/ml arginine
vasotocin (AVT) depolarized Va by 30 mV, decreased FRa by 33%, increased
short-circuit current (Isc) by 17 microA, and increased pHi by 0.17 pH
units. The response of Va, Isc, and pHi occurred concurrently. Forskolin,
theophylline, and 8-(4-chlorophenyl-thio)-adenosine 3',5'-cyclic
monophosphate caused similar changes in Va, Isc, and pHi. The enhanced
response of Isc, Va, and FRa to short pulses of apical amiloride applied
during AVT or cAMP exposure suggests an increase in apical Na+ conductance.
The presence of cAMP agonists also enhanced the response of pHi to
amiloride. We conclude that the AVT- and cAMP-induced increase in Na+
transport across the apical cell membrane is associated with a change in
pHi. These data are consistent with the hypothesis that changes in pHi may
play a role in the second messenger cascade initiated by the antidiuretic
hormone.
