An improved method for combined autoradiography and histochemistry: the simultaneous detection of 6-3H thymidine and acid phosphatase activity in cryostat sections of mouse thymus and duodenum.

A new method is described that enables the simultaneous detection of 6-3H thymidine incorporation and acid phosphatase activity in the same tissue section. Histochemically, naphthol AS B1 released by tissue based acid phosphatase activity from the substrate naphthyl AS B1 phosphoric acid is coupled with a range of diazonium salts to produce insoluble azo dyes. The azo dye tests result in a particulate localization of lysosomal acid phosphatase and also label diffuse sources associated with cell death. The tests selected permit the application of photographic emulsion without the necessity of an inert barrier layer to separate the emulsion from the histochemically treated cryosections. The localization of 6-3H thymidine incorporation and cell death in mouse thymus and duodenum is demonstrated and comparative counts estimating the distribution of 6-3H thymidine incorporation and hydrolase labelled cell death in the thymus are presented. Young mouse thymus (5 weeks) was found to contain 1.36 +/- 0.12% dying cells and 6.78 +/- 0.03% thymidine incorporating cells, whilst old mouse thymus (53 weeks) was found to contain 2.34 +/- 0.6% dying cells and 5.29 +/- 0.37% thymidine incorporating cells.