Effect of ethionine treatment on the activity of enzymes concerned with urea synthesis in rat liver

Abstract

1. The activities of the enzymes of the urea cycle were measured in rat liver after feeding with a diet containing ethionine for 2 weeks. This treatment resulted in a decrease in the activity of ornithine transcarbamoylase, which fell to half the control value, while arginase increased by about 40%. The remaining enzymes of the urea cycle were unchanged at this time of treatment. These results are discussed in relation to the known effects of ethionine on nucleic acid synthesis. 2. The activities of glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were measured in rat liver after feeding with a diet containing ethionine for 2 or 5 weeks. At the shorter time-period glucose 6-phosphate-dehydrogenase activity was more than doubled but 6-phosphogluconate-dehydrogenase activity remained unchanged. 3. The results are compared with similar measurements made after feeding with diets containing 4-dimethylamino-3'-methylazobenzene for 2 weeks. Striking similarities were found in the pattern of change in the enzyme activities of each of the pathways in the two treatments.

Magnesium Deficiency and Urea Cycle Enzymes in Rat Liver.

“…Decreased activity of ornithine transcarbamylase in rat liver has been previously reported in regenerating liver ( 13) in some hepatma.s (14), and in rats fed the amino acid analog ethionine for a periold of 2 weeks (6). These 3 conditions have been associated with increased synthesis of nucleic acids, and in the former two, an increase in the activity of aspartate transarbamylase has also been described, suggesting that the decreased activity of ornithine transarbamylase o c c m d in order to allow an increased incorporation of the carbamyl group into the pyrimidine precursors.…”

Effects of Vanadate on Expression of Liver Arginase in Experimental Diabetic Rats

“…The diabetic state is associated with a notable increase in urea excretion. Increased urea production in diabetes has been demonstrated in vivo, in liver slice preparations, and in isolated perfused liver (11,12). Insulin-dependent diabetes is accompanied by increases in food consumption, amino acid metabolism, and the ratio of blood glucagon to insulin-all factors that tend to increase the activity of the urea cycle.…”