Effect of catecholamines and adrenergic blockade on sodium transport of isolated frog skin

Abstract

The effect of catecholamines and adrenergic blocking agents on Na flux, short-circuit current, and skin resistance was evaluated in isolated frog skin and interpreted according to the alpha and beta adrenergic receptor hypothesis. Alpha adrenergic stimulation (epinephrine following administration of the beta blocking agent pronethalol) decreased net Na flux and short-circuit current to an equivalent degree. Kinetic studies during alpha adrenergic stimulation demonstrated a decrease in rate coefficient for entry into the skin transporting compartment but no change in the rate coefficient presumed to be related to active transport. Beta adrenergic stimulation (isoproterenol or epinephrine following administration of the alpha blocking agent Dibenzyline) produced an equivalent increase in Na influx and outflux with no change in net flux, and development of nonsodium current. The results suggest opposing effects of alpha and beta adrenergic stimulation on Na permeability, although on different pathways for Na movement, i. e., alpha stimulation decreases Na permeability of the epidermal pathways for active transport and beta stimulation increases permeability to Na via another pathway. The beta effects may be related to mucous gland stimulation.