Ultrastructural localization of arylsulfatase C activity in rat kidney

Metal precipitation techniques for ultrastructural demonstration of arylsulfatase C activity were studied in rat kidney. Possible substrates for the techniques were biochemically tested with regard to their velocity of enzymatic hydrolysis and their specificity for arylsulfatase C. Effects of buffers and capturing metals were also examined. The results of these biochemical studies were then verified histochemically. Incubation in a medium containing 1 mM 4-methylumbelliferyl sulfate, 1% barium chloride, 0.1 M imidazole-HCl buffer (pH 7.5), and 5% sucrose achieved identifiable results in adequately fixed kidney. Precipitation of barium sulfate was localized mainly in the endoplasmic reticulum and perinuclear cisterns of the epithelial cells in the descending portions of proximal tubules.