Reduced glucagon induction of tyrosine aminotransferase in perfused livers after ethanol treatment

The increase in hepatic tyrosine aminotransferase activity by ethanol administration involves an acceleration of enzyme synthesis

The present study was conducted to examine the nature of the increase in tyrosine aminotransferase (TAT) activity by acute ethanol administration. A significant rise in aminotransferase activity was observed as early as 1 hr after intact rats were gavaged with ethanol. Ethanol administration also increased TAT activity in adrenalectomized rats. Inhibition of ethanol metabolism by pyrazole administration had no effect on the ethanol-induced increase in TAT activity. Immunochemical analyses revealed that the enhancement of TAT activity in ethanol-fed rats correlated with an increase in aminotransferase protein. Measurement of the rate of TAT synthesis showed that in ethanol-fed rats, [3H]leucine was incorporated into the aminotransferase protein at a higher rate than in controls by a factor which was similar to the enhancement in enzyme activity. Our findings indicate that an acceleration of TAT synthesis fully accounts for the increase in TAT activity during the early stage of enzyme induction. TAT induction by ethanol administration is not dependent upon an increase in adrenal corticosteroid production, nor does it require ethanol metabolism.

Influence of ethanol upon the introduction of tyrosine aminotransferase in liver, upon the NAD content in liver and brain, and upon the activity of glutamate oxalate aminotransferase and glutamate pyruvate aminotransferase in the serum of rats

The influence of ethanol, tryptophan, nicotinamide and methionine upon the activity of glutamate oxalate aminotransferase and glutamate pyruvate aminotransferase in serum as well as the induction of tyrosine aminotransferase in the liver, and of NAD+ + NADH in liver and brain are described. After oral application of 6 g/kg ethanol, the activities of the examined enzymes and the concentrations of NAD+ + NADH in the brain as well as in the liver did not change over a period of 8 hr. Administration of L-methionine lead--as is the case with DL-tryptophan--to a decrease of the NAD+ + NADH-concentration in the brain. A simultaneous application of nicotinamide, DL-tryptophan, L-methionine of l-methylnicotinamide together with ethanol caused a significant increase of the tyrosine aminotransferase induction in adrenalectomized animals. Ethanol reduced the activity of the ADPR transferase in the nuclei of rat liver cells.