The cytochemical demonstration of prostatic acid phosphatase using a new substrate, phosphorylcholine

Prostatic acid phosphatase (PAP), an acid phosphatase specific to the prostate gland, is demonstrated cytochemically for both light and electron microscopy with a new substrate phosphorylcholine. Lead ion is used as capture agent for liberated phosphate ion in a modified Gomori medium. PAP is demonstrated in the tubuloaveolar epithelial secretory cells of the rat ventral prostate gland. In the apical portion of the cell it is found in secretory granules and in the matrix of multivescular bodies. In the Golgi area it is localized in Golgi cisternae, Golgi related vacuoles and multivescular bodies. Evidence is presented that PAP is not a lysosomal enzyme, as are other acid phosphatases, and that phosphorylcholine is a highly specific substrate for PAP. As based on the role of pentavalent nitrogen on substrate structure, it is apparent that PAP is to other acid phosphatases what the cholinesterases are to other esterases.