EFFECT OF INSULIN ON DNA-SYNTHESIS AND KINETIC-PARAMETERS OF THYMIDINE KINASE DURING LIVER-REGENERATION

The effect of insulin on cell proliferation in vivo has been studied i n hepatectomised streptozotocin- diabetic rats. The extent of cell pro liferation in sham and hepatectomized- control diabetic and insulin tr eated rats were monitored by determining DNA content and [H-3]thymidin e incorporation into DNA. The kinetic parameters of thymidine kinase a regulatory enzyme for DNA synthesis was also studied in these groups. The rate of DNA synthesis in liver of streptozotocin -diabetic rats w as significantly higher 24 hrs post-hepatectomy compared to control an d insulin treated diabetic groups. Kinetic studies of thymidine kinase revealed that there was no change in the Michaelis -Menten constant ( K-m) whereas maximum velocity (V-max) was elevated in the diabetic hep atectomized groups compared to control and insulin treated hepatectomi zed groups. Thus our study elucidates the role of insulin in thymidine kinase activity and DNA synthesis.