High density of Ca(2+)-dependent K+ and Cl- channels on the luminal membrane of lacrimal acinar cells.

AUTOR(ES)

Tan, Y P

RESUMO

Tight-seal whole-cell recording and Ca2+ imaging were simultaneously performed on cell clusters or individual acinar cells of rat lacrimal glands during application of the secretagogue acetylcholine. Activation of Ca(2+)-dependent K+ and Cl- currents was selectively followed as a function of time by placing the cell potential near the equilibrium potential for Cl- or for K+ ion, respectively. Upon acetylcholine application to cell clusters, K(+)- and Cl(-)-selective currents displayed a distinctive initial rise ("hump"). At this time, there was only a small elevation of Ca2+ concentration, [Ca2+]i, that was restricted to the luminal end of acinar cells. A quantitative analysis of Ca2+ and current signals during the hump suggested that the luminal membrane contained high densities of K(+)- and Cl(-)-selective channels, roughly 10 times higher than those found in the basolateral domain. Distinct luminal and basolateral membrane domains were preserved in isolated cells, but with less contrasted densities than in cell clusters. The results suggest that Ca(2+)-dependent K+ channels are implicated not only in the transfer of salt from the blood compartment to the interior of acinar cells, as commonly accepted, but also in the electrolyte secretion from the cell interior to the acinar lumen.

Documentos Relacionados

• Ca2+ sensitivity of volume-regulatory K+ and Cl- channels in cultured human epithelial cells.
• Ca(2+)-dependent K+ channels of high conductance in smooth muscle cells isolated from rat cerebral arteries.
• A Ba2+ chelator suppresses long shut events in fully activated high-conductance Ca(2+)-dependent K+ channels.
• Sodium nitroprusside alters Ca2+ flux components and Ca2(+)-dependent fluxes of K+ and Cl- in rat aorta.
• Extracellular nucleotides activate non-selective cation and Ca(2+)-dependent K+ channels in rat osteoclasts.