Prostaglandin E2 enhances the sodium conductance of exocrine glands in isolated frog skin (Rana esculenta)

Summary Prostaglandins are known to stimulate the active transepithelial Na⁺ uptake and the active secretion of Cl^– from the glands of isolated frog skin. In the present work the effect of prostaglandin E₂ (PGE₂) on the glandular Na⁺ conductance was examined. In order to avoid interference from the Na⁺ uptake and the glandular Cl^– secretion the experiments were carried out on skins where the Cl^– secretion was inhibited (the skins were bathed in Cl^– Ringer's solution in the presence of furosemide, or in NO ₃ ^– Ringer's solution), and the active Na⁺ uptake was blocked by the addition of amiloride. Transepithelial current, water flow and ion fluxes were measured. A negative current was passed across the skins (the skins were clamped at –100 mV, basolateral solution was taken as reference). When PGE₂, was added to the skins under these experimental conditions, the current became more negative; this was mainly due to an increase in the Na⁺ efflux. Together with the increase in Na⁺ efflux a significant increase of the water secretion was observed. The water secretion was coupled to the efflux of Na⁺, and when one Na⁺ was pulled from the basolateral to the apical solution via this pathway 230 molecules of water follwed. From the data presented it is suggested that this pathway for Na⁺ is confined to the exocrine glands.