Journal of Applied Physiology, Vol 69, Issue 5 1883-1892, Copyright © 1990 by American Physiological Society
Interaction of heptanol and pressure on sodium and chloride transport by toad skin
M. Li, S. K. Hong, J. M. Goldinger and M. E. Duffey
Department of Physiology, State University of New York, Buffalo 14214.
We examined the interaction of heptanol and hydrostatic pressure on Na+ and
Cl- transport in isolated toad skin. In the presence of Cl-, heptanol
decreased short-circuit current (Isc) and total transepithelial resistance
(Rt). However, in the absence of Cl- in the mucosal bath, heptanol
increased Rt, although it retained the same inhibitory effect on Isc. When
transepithelial active Na+ transport was blocked by amiloride, heptanol had
no effect on Isc whether or not Cl- was present, whereas it decreased the
shunt resistance (Rs) only in the presence of Cl- in the mucosal bath.
Moreover, this effect of heptanol on Rs was significantly smaller in the
presence of diphenylamine-2-carboxylate (DPC), a known Cl- channel blocker.
Pressure also decreased Isc through inhibition of active Na+ transport, but
it increased Rs. When heptanol and pressure were applied together, their
inhibitory effects on Isc were additive, but their effects on Rs were
antagonistic. Furthermore, when a transepithelial Cl- current was produced
by reducing the Cl- concentration of the serosal bath, heptanol stimulated
this current, which was reversibly inhibited by pressure or DPC addition to
the mucosal bath. When the heptanol-stimulated Cl- current was first
inhibited by pressure, subsequent DPC addition had less or no effect. These
results suggest that one site of an antagonistic interaction of heptanol
and pressure in toad skin is an apical membrane Cl- conductance.
