HISTOCHEMICAL DEMONSTRATION OF MITOCHONDRIAL ADENOSINE TRIPHOSPHATASE ACTIVITY IN TISSUE SECTIONS

A comparative study was made of the distribution of mitochondrial adenosine triphosphatase activity in several organs of rat and rabbit using both the calcium and lead techniques. Certain modifications in these techniques assured both improved intracellular morphology and considerable preservation of enzyme activity. Of particular importance was the low temperature (–2 to –3°C) of the neutral calcium-formol solution, and, following short fixation (lead method), a subsequent wash in neutral buffer. Mitochondrial activity was similar with both techniques, but the lead method proved to be less costly, less time-consuming, and above all, far less capricious than the calcium technique. In good preparations, the appearance of mitochondria is as clearly defined as in sections stained with non-enzymatic, conventional techniques. Long exposure of cryostat sections to formalin or preparation of sections from tissue blocks fixed in neutral formalin leads to the complete abolition of mitochondrial activity; on the other hand, it accentuates enzyme staining of other structures, such as, for instance, bile canaliculi in the liver and the secretory capillaries in the pancreas and salivary glands. It also visualizes the infolding membranes in certain tubules of the rat and dog kidney. It is assumed that formalin-fixation aids in the enzymato-morphologic distinction of these two different intracellular structures.