Quantitative Microdetermination of Enzymes in Sweat Gland: V. Ouabain-Sensitive Sodium-Potassium Activated Adenosinetriphosphatase

Abstract

Extract: The excessive concentration of sodium chloride in sweat in cystic fibrosis may be due to failure of a ‘sodium pump’ mechanism. In view of a possible relationship between electrolyte transport and ouabain sensitive ATPase, determination of this enzyme activity was undertaken in isolated sweat gland tissue from cystic fibrosis and control subjects. In each case, determinations were made with optimal Na+, K+ and Mg++ in the substrate mixture, with or without ouabain. With activities expressed as moles phosphate liberated per kg dry sweat gland tissue per hour, seven cystic fibrosis patients gave a mean ouabain sensitive ATPase activity of 2.0 ± 1.1 (SD). Seven controls gave 2.9 ± 1.6. This difference was not significant statistically (t = 1.1). Speculation: Contrary to what might have been suspected from reported results on a relationship between ouabain sensitive ATPase and sodium transport in various sites, namely, crab nerve tissue, avian salt gland, human and sheep erythrocytes and various other tissues, the present study involving skin biopsies from cystic fibrosis patients and controls fails to show this enzyme to be deficient in relation to the defect in sodium transport in the sweat gland in cystic fibrosis.