Calcium modulates transepithelial potassium secretion across isolated frog skin

1. Transepithelial K+ movements across isolated frog skin consist of four components: (i) a passive component; (ii) an active inward transport of K+ which occurs via the epithelial cells; (iii + iv) two active outward-directed components, one via the skin glands, the other via the epithelial cells. 2. Incubation of frog skin in gluconate Ringer's solution activates the K+ secretion via the epithelial cells. 3. A decrease in the Ca2+ activity of the epithelial cells increases the K+ permeability of the apical membrane and reduces the K+ permeability of the basolateral membrane.