Hoechst 33342 staining coupled with conventional histological technique.

Hoechst 33342 was injected either intravenously or intraperitoneally into mice which were killed 1 or 24 hr or 7, 14 or 28 days later. Various organs were fixed and paraffin embedded. Visual inspection showed that independently of the route of dye administration or survival time, distinct fluorescence of nuclei was observed in organs other than cerebral cortex. Even formic acid decalcification of bone failed to abolish the fluorescence of osteocytes. In vivo staining with Hoechst 33342 is proposed as an alternative for staining after sectioning. Cells from spleens of Hoechst 33342-injected mice or stained in vitro were injected intramuscularly into mice. Hoechst 33342-stained splenocytes could be found in deparaffinized sections at the site of injection 24 hr later.