Expression of S-adenosylmethionine synthetase isozyme genes in regenerating rat liver after partial hepatectomy

Mammalian S-adenosylmethionine (AdoMet) synthetase exists as two isozymes, liver-type and non-hepatic-type enzymes. To investigate the possible role of AdoMet synthetase in proliferating cells, we have examined the expression of these two isozyme genes in regenerating rat liver after partial hepatectomy using Northern blot analysis. In normal adult rat liver the non-hepatic-type isozyme mRNA was not detectable, however, when partial hepatectomy was performed, there was an obvious appearance 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 partial hepatectomy with similar time course. These results indicate that these two AdoMet synthetase isozymes may play an important role during the prereplicative phase which precedes DNA synthesis.