ISSN:
1432-2013
Schlagwort(e):
Hepatic nitrogen metabolism
;
Proteolysis
;
Mitochondrial transfer of reducing equivalents
;
Cellular redox state
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Medizin
Notizen:
Summary The nitrogen metabolism was studied in the perfused rat liver under a variety of conditions. Whether pyruvate, alanine or glutamine was the substrate, the total nitrogen balance of the liver could be accounted for by proteolysis, alanine, glutamine, urea and ammonia production, and substrate uptake. When alanine was not added as a substrate, it was produced by the liver at a rate that was a function of the hepatic alanine concentration. Anoxia resulted in a dramatic increase in hepatic alanine production which was accounted for largely by an increased rate of proteolysis. The increased alanine production was probably largely derived from glutamate. However, a decrease in the hepatic glutamate content can not account for the increased alanine output indicating that glutamate had to be synthetized intramitochondrially and transferred to the cytosol. It is suggested then that under certain metabolic conditions, particulary anoxia, the increased alanine production may act as an alternative shuttle mechanism for transferring reducing equivalents from the mitochondria to the cytosol. The mitochondrial [NAD+]/[NADH] ratios were virtually the same when calculated from the glutamate or the β-hydroxybutyrate dehydrogenase reaction, suggesting that both enzymes are in equilibrium with the same mitochondrial pool of nicotinamide nucleotides. Anoxia increased hepatic proteolysis in the presence of pyruvate. These results in the intact organ are in disagreement with previous experiments in subcellular systems, which suggested that proteolysis was decreased by anoxia and increased by the addition of ATP.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00591573
Permalink
