Late phase of liver restoration following partial hepatectomy in phenobarbital-treated rats. II. Effect of phenobarbital on aspartate aminotransferase, alanine aminotransferase, glutamate dehydrogenase, and UDP-glucuronyltransferase activity.

Rats were treated with 50 mg phenobarbital (PB) per kg body weight for 7 days prior to or after partial hepatectomy. The activities of aspartate aminotransferase, alanine aminotransferase, and glutamate dehydrogenase were measured in the regenerating liver 1 week following liver amputation. UDP-glucuronyl transferase activity was determined at the time of surgery as well as 7 days later at the time of death. Alanine aminotransferase was induced by PB in rats only treated in the postoperative period, while aspartate aminotransferase and glutamate dehydrogenase were not. The activity of UDP-glucuronyl transferase was increased more than twofold by repeated PB treatment in both normal and regenerating liver. After cessation of therapy, however, the enhanced activities returned to a normal level. It is concluded that UDP-glucuronyl transferase activity in regenerating liver is as inducible as in normal rat liver by repeated PB treatment despite incomplete hepatic regeneration. Preoperative PB treatment alone is not sufficient to stimulate the glucuronylating pathway in the late phase of liver regeneration.