Liver Enzymes in the Eck Fistula Rat

Abstract
The paper considers whether shunting of portal blood around the liver and decreased total hepatic blood flow are sufficient to explain the degree of hyperammonemia occurring after portacaval shunt (PCS). For this purpose, urea-cycle enzymes, transaminases, and glutamatedehydrogenase were measured in rat-liver homogenates 10, 20, and 30 days after PCS and compared to unoperated controls. In view of the marked postoperative reduction of liver mass, three typical responses could be observed : type I, normal or slightly decreased enzyme activity per gram of liver, but decreased per total liver mass (ornithine carbamyltransferase, argininosuccinate synthetase, arginase, glutamate pyruvate, and oxaloacetate transaminase, glutamate dehydrogenase); type II, increased enzyme activity per gram liver, but decreased per total liver mass (carbamylphosphate synthetase); type III, increased enzyme activity per gram liver but normal per total-liver mass (argininosuccinate cleavage enzyme). Particu - larly, the rate-limiting step of the urea cycle (argininosuccinate synthetase) showed a type-I response. The data suggest that liver ‘atrophy’ after PCS is associated with a reduction of functional enzyme content. This represents at least one factor contributing to hyperammonemia in this experimental model.

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