Abstract
A direct lead method for the visualization of alkaline phosphatase activity at pH 9 was used in a study on the absorptive cells of the duodenum of the mouse. Lead phosphate precipitate was observed in several structures after a short incubation of glutaraldehyde-fixed frozen sections. On microvilli and in vacuoles below the terminal web, the reaction was intense and persisted even after osmic acid fixation. In the Golgi zone, in the smooth reticulum cisternae and in the dense bodies, the reaction was prominent. In these sites, the deposits were not observed after osmic acid fixation or after short incubation in media containing substrates other than β-glycerophosphate or α-naphthylphosphate.