Nonisotonicity of simian eccrine primary sweat induced in vitro

Na+, K+, Cl-, and HCO-3 concentrations were determined in both methacholine (MCh)-induced and isoproterenol (ISO)-induced primary sweat collected directly from isolated and cannulated rhesus monkey palm eccrine secretory coils in vitro. Na+ concentration [( Na+]) of MCh-induced sweat was higher than that of the bathing medium by 4.2 mM, i.e., 155.4 vs. 151.2 mM. Sweat [Cl-] was consistently higher than that of the medium by 13.7 and 11.2 mM in both MCh- and ISO-induced primary fluid, respectively. The sweat-to-bath Cl- gradient increased as [Cl-] in the bath was lowered by substituting with less-permeable anions. In contrast sweat [HCO-3] was much lower in both MCh- and ISO-induced sweat than that of the bathing medium, i.e., approximately 6 mM in sweat vs. 25 mM in the bath. [K+] in MCh-induced primary sweat (mean of 6.63 mM) was consistently higher than that of the bathing medium (5 mM). Furthermore, [K+] tended to be the highest in the first sweat sample after MCh stimulation, reaching as high as 9 mM. In sharp contrast ISO-induced primary sweat showed [K+] that was almost always less than 5 mM with the mean of 4.03 mM. These electrolyte profiles of the primary fluid have been discussed relative to the transport model generally applied for Cl- secretory epithelia.