AJP - Regulatory, Integrative and Comparative Physiology, Vol 242, Issue 5 465-R470, Copyright © 1982 by American Physiological Society
Uridine regulation by the isolated rat liver: perfusion with an artificial oxygen carrier
A. Monks and R. L. Cysyk
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.
