HISTOCHEMICAL DEMONSTRATION OF THE SOLUBLE ENZYME, KETOSE REDUCTASE (SORBITOL DEHYDROGENASE), BY UTILIZING A NEW FIXING SOLUTION

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Abstract
Localization of the activity of the soluble enzyme, ketose reductase, was made possible by using a high-tonicity fixative containing formalin, ethanol, and tris (hydroxymethyl)aminomethane and by maintaining high tonicity in the incubating medium. Incubations could be performed at pH 8.8, an optimal pH for the conversion of sorbitol to fructose. False localization, probably resulting from diffusion of the first reactions product, reduced nicotinamide adenine dinucleotide, was minimized by slowing the reaction rate and using less tissue in the incubating medium. When this medium was tested with phenazine methosulfate, neither reduced nicotinamide adenine dinucleotide nor soluble dehydrogenase activity was detected. Ketose reductase activity was demonstrable throughout the epithelia of the seminal vesicle and the coagulating gland of the mouse. The activity was greater in the coagulating gland. It also was present in spermatozoa, central hepatic parenchymal cells, and renal proximal tubule. It was not present in the vas deferens epithelium nor ganglion cells. Reactivity in smooth muscle was believed to be artifact.