RESUMO
A study was made of the change in arylamine acetyltransferase(AAT) activity in regenerating and/or cholestatic rat livers. Cytosolic, mitochondrial and microsomal AAT activities were determined over a period of 10 days in rat livers which were regenerating after 70%(median and left lateral lobes) partial hepatectomy and over a period of 42 days in rat livers with cholestasis induced by a common bile duct ligation. The values of Km and Vmax in these hepatic enzymes were measured. Both the cytosolic and the microsomal AAT activities in the regenerating rat livers showed significant increases from the first day to the third day after the partial hepatectomy. However, the mitochondrial AAT activity did not change. The cytosolic and the microsomal AAT activities in the cholestatic rat livers showed a significant increase on the first day and from the first day to the second day, respectively after the ligation; Both the cytosolic and the microsomal AAT activities showed significant decreases from the fourteenth day to the forty-second day after the ligation. However, the mitochondrial AAT activity did not change. The Vmax values of both the cytosolic and the microsomal AAT activity in the regenerating and/or cholestatic rat livers showed significant increases on the first day after the partial hepatectomy and/or the ligation. However, the Vmax values of both the cytosolic and the microsomal AAT activities in the cholestatic rat livers showed significant decreases on the twenty-eighth day after the ligation. On the other hand, the Km values of the above enzymes did not change. In view of the above results, the AAT activity in the regenerating rat liver appears to be due to the enzyme increasing its biosynthesis in the regenerating stage. The AAT activity in the cholestatic rat liver suggests that the enzymes is increasing its biosynthesis in the severe necrotizing stage, but decreasing its biosynthesis severe hepatic dysfunction stage.