Uridine regulation by the isolated rat liver: perfusion with an artificial oxygen carrier.
The isolated rat liver was used to investigate the role of the liver in the regulation of circulating uridine concentrations. A synthetic blood substitute (Fluosol-43) was utilized as an alternative oxygen-carrying perfusion medium to a simplified blood preparation and produced no apparent hepatotoxicity within the perfusion period. The isolated rat liver excreted uridine into a circulating perfusion medium achieving concentrations similar to those found in rat plasma (1.4 +/- 0.6 microM). The mean output of uridine over 2 h was 107 nmol.h-1.g liver-1, but if the perfusate was recirculated the net output of uridine was reduced to 12.7 nmol.h-1.g-1. The rate of depletion of nonphysiological concentrations of circulating uridine was found to be concentration dependent up to 25 microM. At a steady state of circulating uridine, a radioactive uridine spike was cleared with a half-life of 7.4 min and an elimination constant of 0.094 min-1; 30% of the radioactivity appeared in the perfusate as metabolites of uridine within 40 min. Thus the perfused rat liver acts to maintain circulating uridine concentrations similar to those measured in plasma.
D000818:Animals; D004912:Erythrocytes; D005466:Fluorocarbons; D008099:Liver / Q000378:metabolism / Q000502:physiology*; D008297:Male; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D014529:Uridine / Q000032:analysis / Q000096:biosynthesis / Q000502:physiology*
D005466:Fluorocarbons; C008807:perfluorotributylamine; D014529:Uridine