Origin of periodic acid-Schiff-reactive glycoprotein in human eccrine sweat

To evaluate the possible involvement of ductal blockade with periodic acid-Schiff (PAS)-positive materials in the mechanism of hidromeiosis in humans, skin slices were incubated with methacholine for 2 h and PAS-positive materials localized histologically in the ductal lumen. In 20% of the glands complete ductal blockade with PAS-positive materials was noted. The characteristics and origin of such PAS-positive glycoproteins in human sweat were then studied using various electrophoretic techniques. One-dimensional sodium dodecylsulfate-polyacrylamide gel electrophoresis (1-D SDS-PAGE) demonstrated considerable individual variation in the electrophoretic pattern; however, four major bands at 45, 28, 20, and 18K shared by different individuals, were PAS positive. Further studies using two-dimensional SDS-PAGE, immunodiffusion and immunoaffinity chromatography demonstrated that the PAS-positive glycoproteins are not derived directly from serum because they are electrophoretically and antigenically distinct from serum proteins, including alpha 1-glycoprotein, alpha 2-HS-glycoprotein, and alpha 1-antitrypsin. Since only dark cell granules are densely stained in the histochemical PAS staining, and because antiserum produced against the PAS-positive band selectively stained cells facing the secretory coil lumen (which are most likely dark cells), it is suggested that PAS-positive sweat glycoproteins are derived predominantly from the dark cells.