Spontaneous sweat secretion in calcium-free strontium medium.

Sr2+ substitutes for Ca2+ in methacholine (MCH)-evoked sweat secretion in isolated simian eccrine sweat glands, but four to eight times greater concentrations of Sr2+ were required to achieve the same effect as did a given Ca2+ concentration. In Ca2+-free Sr2+ medium the anticholinergic effect of atropine was reduced by about four orders of magnitude. In the Sr2+ medium, spontaneous sweat secretion (SSS) was also observed in the absence of any pharmacological stimuli. SSS occurs slowly, reaching a plateau after 30 min incubation. The maximal SSS is a saturation function of Sr2+ concentration reaching a maximum at 8 mM. Sr2+-induced SSS was inhibitable by removal of Sr2+, low bath temperature (10-14 degrees C), ouabain (5 X 10(-6) M), and D 600 (10(-3) M). Ca2+ was found to inhibit Sr2+-induced SSS, but a Schild plot for the Ca2+ and Sr2+ dose relationship failed to show a slope of unity. The data suggest that Sr2+-induced SSS represents actual secretory processes, which are triggered by Sr2+ leaking into the cell through as yet undefined membrane channels.