Voltage and Ca²⁺-activated K⁺ channel in baso-lateral acinar cell membranes of mammalian salivary glands

Nervous or hormonal stimulation of many exocrine glands evokes release of cellular K⁺ (ref. 1), as originally demonstrated in mammalian salivary glands^2,3, and is associated with a marked increase in membrane conductance^1,4,5. We now demonstrate directly, by using the patch-clamp technique⁶, the existence of a K⁺ channel with a large conductance localized in the basolateral plasma membranes of mouse and rat salivary gland acinar cells. The K⁺ channel has a conductance of ∼250 pS in the presence of high K⁺ solutions on both sides of the membrane. Although mammalian exocrine glands are believed not to possess voltage-activated channels^1,7, the probability of opening the salivary gland K⁺ channel was increased by membrane depolarization. The frequency of channel opening, particularly at higher membrane potentials, was increased markedly by elevating the internal ionized Ca²⁺ concentration, as previously shown for high-conductance K⁺ channels from cells of neural origin^8-10. The Ca²⁺ and voltage-activated K⁺ channel explains the marked cellular K ⁺ release that is characteristically observed when salivary glands are stimulated to secrete.