Possible Significance of Changes in the Energy Metabolism for the Release of Liver Lactate Dehydrogenase and for the Uptake and Incorporation of [¹⁴C]-Orotic Acid into Liver Ribonucleic Acid after Partial Hepatectomy

Abstract

The mouse liver revealed no increased incorporation of [¹⁴C]-orotic acid into either the total acid-soluble fraction, the uridine triphosphate or the RNA at 6 and 24 h after partial hepatectomy. In regenerating mouse and rat liver, the concentration of adenosine triphosphate was decreased 15–20% at 6 h, but was in the same range as that of the controls at 24 h. The adenosine monophosphate concentration of mouse liver increased 4-fold and 2-fold at these times after partial hepatectomy, respectively. The results indicate no direct relationship between the energy metabolism and the uptake and incorporation of orotic acid into RNA of regenerating liver. The activity of mouse plasma lactate dehydrogenase 5 (LDH 5) was increased 12-fold at 6 h and 5-fold at 24 h after partial hepatectomy. In rat, the LDH 5 activity was increased 2-fold at 6 h but was not different from that of the controls at 24 h. An increased leakage of LDH 5, possibly related to the decreased energy content of the liver, was thus revealed by the partially hepatectomized mice.

RNA synthesis in regenerating mouse liver evaluated by incorporation of [methyl-14C]methionine and by determination of RNA polymerase activity

“…The increased synthesis of rRNA in regenerating mouse liver cannot be demonstrated by incorporation of labelled orotic acid (Yngner et al, 1979a(Yngner et al, , 1980. In regenerating rat liver, however, an increased transcription has been shown with this method (Bresnick, 1971;Bucher & Malt, 1971;Lewan et al, 1977).…”

“…In contrast with regenerating rat liver, mouse liver reveals no enhanced uptake of orotic acid or incorporation of this precursor into either UTP or RNA at 6 and 24h after partial hepatectomy (Yngner et al, 1979a(Yngner et al, , 1980, nor is there an increased incorporation of labelled uridine into UTP or RNA of regenerating mouse liver, despite an increased uptake of the precursor into the total acid-soluble fraction (Yngner et al, 1979b).…”