Induction of Tyrosine Aminotransaminase and Ornithine Decarboxylase in Isolated Perfused Regenerating Rat Liver*

Abstract

Tyrosine transaminase [L-tyrosine: 2-oxoglutarate aminotransferase, EC 2.6.1.5] and L-ornithine decarboxylase [EC 4.1.1.17] were induced in the liver of adrenalectomized rats by partial hepatectomy. The induction of these enzymes in regenerating liver is, therefore, not due to changes in the glucocorticoid concentration in the blood caused by stress. Using these enzyme activities as parameters of early biochemical events induced by partial hepatectomy, the conditions necessary for the regenerative process in isolated, perfused liver were investigated. Neither enzyme was induced on perfusion with synthetic medium. However, ornithine decarboxylase was induced on perfusion with serum, even without partial hepatectomy, although it was induced to a greater extent in partially hepatectomized liver. Tyrosine transaminase was induced in isolated liver perfused with medium containing serum, only when more than 70y–80% of the liver had been removed. Thus, it was concluded that in isolated, perfused liver, both the addition of serum to the perfusion medium and partial hepatectomy were necessary to induce the two enzymes.