Functions of calcium in sweat secretion

Abstract

CALCIUM is an important regulatory factor in many physiological systems, including fluid-transporting epithelia. There is good evidence that such regulatory factors are involved in normal secretory function¹, and indirect evidence that they may be involved in secretory irregularities in disease states^2,3. Using a novel in vitro preparation, we have examined the effects of calcium on the secretory properties of the human eccrine sweat gland. The sweat gland consists of a single coiled tubule which is closed at the proximal secretory end and open at the distal re-absorptive end. On stimulation, the secretory portion of the tubule secretes an isotonic precursor fluid from which NaCl is absorbed hypertonically in the distal, re-absorptive duct. The final secretory product, hypotonic sweat, is excreted on to the epidermis for evaporation. We have found that calcium is an essential requirement for stimulating sweat and that this ion may be a factor in regulating the hypotonicity of sweat.