Effect of a lipid extract of frog skin on short-circuit current and sodium transport of isolated frog skin

Abstract

Lipid extracts obtained from frog skin and shown by thin-layer chromatography to contain materials with R F values of cholesterol, cholesteryl linoleate, lecithin, palmitic acid, tripalmitin, and a number of methylated fatty acids stimulated short-circuit current and net sodium isotope flux of isolated frog skin. In contrast to the delayed response to adrenal steroids, the rise in short-circuit current was almost immediate. Change in net sodium flux was due entirely to rise in sodium influx. Sodium outflux was not stimulated, as it is by catecholamines. Treatment with the extract rendered the skins almost completely refractory to a second dose of extract but did not impair responsiveness to acetylcholine. Similarly, treatment of the skins with acetylcholine rendered them insensitive to a second dose of acetylcholine but not to the extract. Atropine failed to block the stimulatory action of the extract. These observations suggest that the extracts contained an agent or agents which are part of the natural sodium transport mechanism, which are not unaltered adrenal steroids, catecholamine, nor acetylcholine and whose actions are not mediated by these substances.