Transepithelial potential during strontium-induced spontaneous sweating.

Transepithelial electrical potential difference (PD) of the secretory portion of the rhesus monkey palm eccrine sweat gland was studied in both Ca2+-containing (control and Ca2+-free Sr2+ media. In the control medium, the luminal PD was a saturation function of the methacholine (MCH) concentration, reaching a plateau at about -6 mV (lumen negative) at 10(-5) M MCH. In the Sr2+ medium, the luminal PD increased spontaneously with a time course similar to that the spontaneous sweat secretion (SSS). Like SSS, the spontaneous luminal PD in the Sr2+ medium is a saturation function of the Sr2+ concentration in the bath, reaching a plateau at -9 mV at 8 mM Sr2+. Addition of MCH to the Sr2+ medium caused a rapid increase in the lumen-negative PD as seen in the control medium. The spontaneous lumen-negative PD was abolished by subsequent addition of Ca2+ to the bath, as was the SSS [K. Sato, Am. J. Physiol. 239 (Cell Physiol. 8): C90-C97, 1980]. The data further reinforce the notion that Sr2+-induced SSS represents true secretory processes which are triggered by Sr2+ leaking into the cell bypassing the receptor-agonist interaction.