The ultrastructural cytochemistry of lactic dehydrogenase, succinic dehydrogenase, dihydro-nicotinamide adenine dinucleotide diaphorase and cytochrome oxidase activities in hair cell mitochondria of the guinea pig cochlea.

The use of cinnamyl nitroblue tetrazolium chloride (DS-NBT) in dehydrogenase experiments (lactic dehydrogenase, succinic dehydrogenase, nicotinamide adenine dinucleotide diaphorase) and 3,3'-diaminobenzidine tetrahydrochloride (DAB) in cytochrome oxidase experiments indicated that mitochondrial oxidoreduction reactions from nicotinamide adenine dinucleotide to cytochrome oxidase are located on the inner mitochondrial membrane in the outer compartment and the intracristate spaces. These reactions behave according to the chemiosmotic hypothesis. The cochlear hair cell mitochondria are cytochemically indistinguishable from free liver mitochondria. The heterogeneous mitochondrial staining pattern is related to the osmolarity of the incubation media, solubility of the enzymes and pH of the medium, but not to the fixation method.