Isozymes of nuclear protein tyrosine kinase during chemical induced hepatocarcinogenesis in rats.

The activity changes of isozymes of nuclear protein tyrosine kinase (nPTK) during chemically induced hepatocarcinogenesis in rats was studied. Two isozymes were isolated from rat liver by using ion exchange chromatography. These two isozymes were designated as nPTK-I and nPTK-II, and were found to be minor and major components of total nPTK respectively. These proved to be two different enzymes due to their different characteristics, such as molecular weights, electrical charges and kinetics. The specific activity nPTK-I and its percentages in total nPTK significantly increased in preneoplastic stage (week 10) and slightly elevated further in neoplastic stage (week 18). The specific activity of the nPTK-II moderately increased at week 10, but compared to its value at week 10, it decrease at week 18, resulted in gradual decrease of its percentage in total nPTK. These results indicate that rat hepatic nPTK-I and nTPK-II may be related to neoplastic and preneoplastic stages of rat liver respectively.