Late phase of liver restoration following partial hepatectomy in phenobarbital-treated rats. I. Effect of preoperative and postoperative phenobarbital treatment on organ weight, protein and DNA content of the normal and the regenerating liver.

Rats were treated with phenobarbital (50 mg/kg) for 7 days prior to or after partial hepatectomy. Liver weight, protein, DNA, and RNA content were determined in liver tissue removed at operation as well as in regenerating liver 7 days later at the time of death. When rats were treated with phenobarbital in the preoperative period an increase in liver weight secondary to cell hyperplasia was observed as compared to livers of rats treated with sodium chloride. The weight of regenerating liver of preoperatively treated rats did not differ from the controls, but protein concentration was significantly higher (P less than or equal to 0.001). When phenobarbital was applied only in the postoperative period, a highly significant (P less than or equal to 0.001) enlargement of the regenerating liver tissue was found secondary to cell hypertrophy without hyperplasia, whereas protein concentration was unchanged. An increased RNA/DNA ratio, however, suggests that further protein synthesis is enhanced. The results show that both preoperative and postoperative phenobarbital treatment aids in hepatic tissue enlargement, though by a different mechanism.