Influence of extracellular bicarbonate on the short‐circuit current and intracellular free calcium of human cultured sweat duct cells

Abstract

SUMMARYTransepithelial short-circuit current (Is() and intracellular free Ca2l (Call) was studied in monolayers of cultured human sweat duct cells (CSDCs) in the presence or absence of HCO3-(and CO2) in the bathing solutions. Addition of HCO3-(and C02) increased the control IS,, by more than 50 %. The effect of HCO3-(and C02) on ISCC was confined to the serosal bath. The HCO3-(and C02) effect was also studied during stimulation with the cholinergic agonist methacholine (MCh), which in CSDC induces a complex response consisting of an initial ISCC and Ca2+ spike, which is independent of extracellular Ca2 , followed by regular IS(C and Ca2+ oscillations, which are absent during Ca2+-free bathing conditions. The sustained ISC and Ca2+ oscillations, but not the initial ISC( and Ca2+ spike, were abolished by the removal of extracellular HCO3-(and C02). It is concluded that the Ca2+ influx and the I, in CSDCs are critically influenced by the presence of extracellular HCO3-(and C02) in the bathing solutions.