AJP - Renal Physiology, Vol 233, Issue 2 94-101, Copyright © 1977 by American Physiological Society
Effect of the ionophore A23187 on chloride transport across isolated frog cornea
O. A. Candia, R. Montoreano and S. M. Podos
The ionophore A23187 at a concentration of 10(-7) to 10(-5) M stimulated
active transport of Cl across the isolated frog cornea. The ionophore had
no effect in a Cl-free medium. Both unidirectional Cl fluxes were increased
by A23187. The electrical resistance was decreased, and this can be totally
accounted for by the increment in passive Cl fluxes. The effect of A23187
on Cl transport and permeability mimicked the effects of cyclic AMP,
isoproterenol, and epinephrine. A23187 had no effect when the corneas were
fully stimulated by epinephrine or isoproterenol. A23187 produced normal
stimulation of the SCC in corneas pretreated with alpha- and
beta-adrenergic blockers. The stimulation of the SCC by A23187 was
dependent on the presence of Ca in the Ringer solution. Excess Ca (10 mM)
resulted in a reduced response. Increasing the Mg concentration in the
medium reduced the stimulation of the SCC with Ca concentrations of 0.1-5
mM, but prevented the relative inhibition of 10 mM Ca. Intracellular Ca
concentration seemed to regulate Cl permeability of the cornea.
