EXPRESSION OF S-ADENOSYLMETHIONINE SYNTHETASE ISOZYME GENES IN REGENERATING RAT-LIVER AFTER PARTIAL-HEPATECTOMY

Mammalian S-adenosylmethionine (AdoMet) synthetase exists as two isozy mes, liver-type and non-hepatic-type enzymes. To investigate the possi ble role of AdoMet synthetase in proliferating cells, we have examined the expression of these two isozyme genes in regenerating rat liver a fter partial hepatectomy using Northern blot analysis. In normal adult rat liver the non-hepatic-type isozyme mRNA was not detectable, howev er, when partial hepatectomy was performed, there was an obvious appea rance of the non-hepatic-type enzyme mRNA after operation. The levels of non-hepatic-type isozyme mRNA was peaked at 4 h and maintained the level at least till 8 h after operation, then decreased. In addition, the liver-type AdoMet synthetase gene expression was also induced by p artial hepatectomy with similar time course. These results indicate th at these two AdoMet synthetase isozymes may play an important role dur ing the prereplicative phase which precedes DNA synthesis.