A permeability test for the study of mitochondrial injury in in vitro cultured heart muscle and endothelioid cells.

A cytochemical permeability test for the detection of injury to in situ mitochondria of cultured heart cells is presented. The test is based on the increased rate at which injured mitochondria stain for succinate dehydrogenase activity. Whereas an intact inner mitochondrial membrane limits the rate at which Nitro Blue tetrazolium and phenazine methosulphate reach succinate dehydrogenase, injured mitochondria allow these reactants to reach the enzyme more rapidly to form microscopically-observable formazan granules. The extent of staining at fixed durations of incubation with the reactants was assessed on a blind basis with pseudo dark-field microscopy, using a standardized rating scale. Differences in the staining of control and treated cells were analysed statistically by a semi-quantitative method. Treatment of the cultures with either vitamin A or chlorpromazine, resulted in more rapid mitochondrial staining. Brief pre-fixation of the cells with cold acetone also labilized the mitochondria as did a delay in the change of culture medium.