Effect of Growth Hormone upon the RNA Polymerase and Deoxythymidine Kinase Activities of Regenerating Liver in Hypophysectomized Rats

Regenerating rat liver showed markedly increased nuclear, nucleolar and chromatin RNA polymerase [EC 2.7.7.6] activities 6 hr after partial hepatectomy. Deoxy-thymidine kinase [EC 2.7.1.21] activity began to increase 20–24 hr after partial hepatectomy. However, after hypophysectomy and partial hepatectomy these enzymeactivities did not show corresponding increases. Treatment of hypophysectomized rats with growth hormone before partial hepatectomy resulted in increases in the RNA polymerase and deoxythymidine kinase activities 6hr and 20 hr, respectively, after partial hepatectomy. These results suggest that the growth hormone may be involved in initiation of liver regeneration.