AJP - Cell Physiology, Vol 255, Issue 3 C357-C367, Copyright © 1988 by American Physiological Society
Effects of oxytocin on cation content and electrophysiology of frog skin epithelium
H. F. Schoen, A. Kaufman and D. Erlij
Department of Physiology, Downstate Medical Center, Brooklyn, New York 11203.
We measured effects of oxytocin on current-voltage (I-V) relations of frog
(Rana catesbeiana) skins impaled with an intracellular microelectrode. In
both Cl- and Cl(-)-free (SO4(2-) solutions, oxytocin caused an approximate
doubling short-circuit current (Isc) and a depolarization of the cell
membrane. Increase in apical membrane slope conductance, chord conductance,
and permeability after oxytocin correlated with the increase in
amiloride-sensitive Isc. Oxytocin also increased basolateral membrane
conductance (gb). In Cl-, the shift in the voltage intercept of the apical
membrane I-V relation (Ea) implied increased intracellular Na+ activity
(a(Na)c) after oxytocin. In isolated frog skin epithelia, a similar
increase in intracellular [Na+] after oxytocin was demonstrated by flame
photometry. In SO4(2-), changes caused by oxytocin in both Ea and in flame
photometrically determined cell [Na+] were minimal. The voltage intercept
of the basolateral membrane I-V relations (Eb) was shifted by oxytocin in
both Cl- and SO4(2-) solutions. Assuming that the basolateral membrane is
selectively permeable to K+, changes in K+ obtained from Eb were in
disagreement with those obtained by flame photometry. These results suggest
that 1) the increase in a(Na)c caused by oxytocin is not essential to
produce either the increase in gb or Isc and 2) ions other than K+ make an
important contribution to basolateral membrane conductance.
