An improved procedure for the X-ray microanalysis of acid phosphatase activity in lysosomes

The useful detection of acid phosphatase activity with cerium as a capturing agent is confirmed. By introducing a freeze step in combination with a preincubation, reliably localized, lysosomal precipitates are obtained and aspecific ones prevented. Short (t less than 1 h) postfixation with either OsO4 plus K4Fe (CN)6 or OsO4 plus aminotriazole, added to lysosomal cerium localization a high membrane contrast. The detection of cerium by X-ray microanalysis is improved by a better spectral separation of the osmium (M alpha) and cerium (L alpha) peaks.