Sodium and Chloride in Eccrine Sweat of Men and Women During Training with Acetyl-B-Methylcholine**From the Human Environmental Research Unit, Department of Physiology and Biophysics, University of Illinois, Urbana, Illinois 61801.

ABSTRACTSweat glands in a small area of skin on the volar surface of the forearm were stimulated twice daily with intradermal injections of acetyl-B-methylcholine. Training, resulting in an increased sweating response to the standard dose of drug, occurred in all of the five men and five women subjects. Sweat samples were collected on filter papers in an unventilated sweat capsule and analyzed for sodium and chloride. Both of these minerals increased in concentration as the sweat rate increased. In eight subjects the increase in sodium was that which would be predicted on the basis of enhanced activity of the sweat glands involved. In two cases the sodium increased less than would be expected if the increased sweat were due to training alone. This was attributed to the recruitment of additional sweat glands, which resulted in a greater volume of sweat with less tonicity than expected.The women were less sensitive to the standard dose of acetyl-B-methylcholine used throughout the training period. The data from men and women were significantly different on days one and two and on days nine and ten. However, by the 17th and 18th days of training there was some overlap in data from the two groups