CYTOCHEMICAL DEMONSTRATION OF ORNITHINE CARBAMOYLTRANSFERASE ACTIVITY IN LIVER MITOCHONDRIA OF RAT AND MOUSE

In order to demonstrate ornithine carbamoyltransferase activity cytochemically, thin slices of liver and kidney of rat and mouse were fixed in cold acetone or formol-calcium, and incubated in a medium containing l-ornithine, carbamoyl phosphate, Tris-maleate buffer (pH 7.2), lead nitrate and sucrose. The specific reaction product occurred in the mitochondria of the hepatocytes only, and not in other cells of the liver or kidney. The specificity of the reaction was supported by the following observations. (1) The mitochondrial reaction was not obtained in sections incubated in a medium from which ornithine was omitted. (2) Other amino acids gave no reaction. (3) p-Chloromercuribenzoate suppressed the reaction. (4) The hepatocytes of chick (uricotelic) did not give the reaction. A nonspecific reaction in lysosomes and brush borders is caused probably by acid and alkaline phosphatase activities.