Immunohistochemical analysis of ratS-adenosylmethionine synthetase isozymes in developmental liver

Mammalian S-adenosylmethionine (AdoMet) synthetase exists as two isozymes, liver-type and kidney(non-hepatic)-type enzymes. The developmental expression of these two isozyme proteins has been investigated in rat liver using immunohistochemical techniques. The liver-type AdoMet synthetase is expressed only in adult liver, but not in fetal liver. On the other hand, the kidney-type AdoMet synthetase is predominantly expressed in fetal liver and faintly detected in adult liver. It was also found that both isozymes were localized to the hepatocytes of rat liver. These results clearly show that AdoMet synthetase isozymes are developmentally regulated within hepatocytes. In addition, in rat kidney we have shown that the kidney-type AdoMet synthetase is predominantly localized to the distal tubule.