The ultracytochemical demonstration of a formaldehyde-resistant dehydrogenase of leuco nitroxyl analogues.

A dehydrogenase which is relatively stable in formaldehyde fixative is demonstrated ultracytochemically by the reduction of various leuco nitroxyl analogues in rat hepatic, renal, myocardial, skeletal muscle and prostatic tubuloalveolar glandular tissues. The nonosmiophilic tetrazolium salt, t-(2'-benzothiazolyl)-5-styryl-3-(4'-phtalhydrazidyl) tetrazolium chloride, is subsequently reduced to an insoluble osmiophilic formazan by the hydrogen ions resulting from the dehydrogenase activity. Exposure of the formazan to osmium tetroxide results in electron density enabling visualization of the reaction product in the electron microscope. Known inhibitors of various dehydrogenases were utilized in an attempt to determine the existence and/or extent of any specific characteristics of the dehydrogenase(s) involved.