The effect of calcium on sodium transport by frog skin.
Calcium added to the solution bathing the outside of isolated frog skin caused a reversible decrease in net sodium transport across the skin. At constant sodium concentration, the inhibition of transport increased with increasing calcium concentration, but approached a limiting value. This maximum degree of inhibition was found to depend on sodium concentration; sodium transport could be inhibited by 60 per cent at 96 mM sodium, but by only 18 per cent at 19 mM sodium. The relative effectiveness of a given calcium concentration was also greater the higher the sodium concentration. The unidirectional flux of chloride across the short-circuited skin was decreased by calcium to approximately the same degree as active sodium transport. The results have been interpreted in terms of a relatively non-specific decrease in permeability of the outward facing membrane of the transporting cells. The resulting decrease in sodium permeability apparently causes a decrease in active sodium transport by reducing the availability of sodium to the transporting system.
D000818:Animals; D001001:Anura; D001692:Biological Transport; D001693:Biological Transport, Active; D002118:Calcium / Q000494:pharmacology*; D002712:Chlorides; D017136:Ion Transport; D010539:Permeability; D012867:Skin; D012879:Skin Physiological Phenomena; D012964:Sodium / Q000378:metabolism*
D002712:Chlorides; D012964:Sodium; D002118:Calcium
CALCIUM/pharmacology; SKIN/physiology; SODIUM/metabolism