The consumption of oxygen by slices of kidney tissue of dogs made hypertensive by the Goldblatt technique was studied manometrically. The respiration of the ischemic kidney tissue was found to be much less than that of the normal kidney. Further, a marked reduction in oxidizing ability, as measured by the oxygen uptake and ammonia formation in the presence of the added amines and amino acids, tyramine, isoamylamine, dl-alanine, and l-aspartic acid, was observed.
Extracts of the kidneys were made and tested for amine oxidase, amino acid oxidase, and polyphenol oxidase activity by measuring the increased oxygen consumption and ammonia formation in the presence of the substrates listed above with the addition of l-epinephrine, histamine, and dl- and l-dihydroxyphenylalanine. The preparations from ischemic kidneys of dogs and rabbits showed much lower activity. Animals with varying degrees of constriction of the renal arteries and therefore varying degrees of renal ischemia were prepared and studied. The results with these animals suggested a direct relationship between the degree of renal ischemia and the decrease in oxidizing power of the tissue.
The product of the enzymic oxidation of tyramine was identified as p-hydroxyphenylacetaldehyde by isolation as the dinitrophenylhydrazone of p-hydroxyphenylacetaldehyde.