Effectiveness of THAM in Preventing Cellular Damage Resulting From Oxygen Lack. ∗

Abstract

Summary and conclusions

The effects of oxygen lack on rat liver were studied in order to: (a) compare the results of a variety of methods of producing oxygen lack; (b) evaluate the role of increased intracellular acidity in production of anoxic cell damage; (c) determine if buffering with an intracellular hydrogen ion acceptor reduces the damaging effects of anoxia on cellular metabolism.

The criteria used to establish the severity of cellular damage included; (a) reduction in the activities of 2 mitochondrial enzymes (succinic dehydrogenase and malic dehydro-genase) and of one microsomal enzyme (glu-cose-6-phosphatase); (b) the labilization of 2 lysosomal enzymes (acid phosphatase and cathepsin); (c) the degradation of protein.

Oxygen lack of equivalent duration produced by ischemia in vivo, autolysis in vitro, pump ventilation with a 5% oxygen mixture, and incubation of liver slices in a nitrogen atmosphere caused approximately the same degree of cellular damage: (a) oxygen lack resulted in an early and progressive decrease in the activity of the 2 mitochondrial enzymes and glucose-6-phosphatase activity; (b) the total activities of the 2 acid hydrolases were not affected even by prolonged periods of anoxia, but the free activities of these enzymes were increased by prolonged periods of anoxia; (c) anoxia was associated with a progressive decrease in the titratable buffer capacity and pH of the liver. These studies indicate that acidity is one of the major destructive factors affecting cell metabolism during oxygen lack.

Similar enzymatic and chemical changes were observed in liver slices incubated in an oxygenated medium at low pH's and in a nitrogen atmosphere in a medium buffered to pH 7.4.

THAM buffering largely prevented the early effect of anoxia on the mitochondrial, microsomal and lysosomal enzyme and on protein, but was not effective after long periods of anoxia. Thus it appears the early effect of anoxia on mitochondrial and microsomal enzymes and on protein is due largely to increased acidity.