AJP - Gastrointestinal and Liver Physiology, Vol 245, Issue 6 769-G774, Copyright © 1983 by American Physiological Society
Effects of hematocrit on oxygenation of the isolated perfused rat liver
G. L. Riedel, J. L. Scholle, A. P. Shepherd and W. F. Ward
The isolated perfused rat liver is used ubiquitously for metabolic and
endocrine studies of hepatic function, yet few data are available regarding
the inadequacy of the oxygenation of such preparations. Moreover, the
isolated rat liver is usually deprived of its arterial supply and perfused
via the hepatic portal vein with low-hematocrit or cell-free solutions. To
investigate the efficacy of the oxygen supply, we determined the effect of
hematocrit on the relation between oxygen consumption and perfusate flow.
We then attempted to define a hematocrit at which hepatic oxygenation was
maximal. Livers of male rats anesthesized with pentobarbital sodium were
perfused via the portal vein with fresh canine red blood cells suspended in
Krebs-Ringer-bicarbonate buffer. Perfusions were carried out at various
flow rates, and the relation between perfusate flow and oxygen uptake was
determined. At flow rates above 100 ml X min-1 X 100 g liver-1, oxygen
uptake was independent of flow but below that value was flow limited,
regardless of whether the hematocrit was 10, 20, or 40%. To determine the
optimal hematocrit for hepatic oxygen uptake, hepatic portal venous and
hepatic venous pressures were held at 10 and 0 mmHg, respectively. The
hematocrit was lowered in steps from 80 to 10%. Blood flow increased
exponentially as hematocrit fell while oxygen uptake increased to a maximum
at approximately 20%. It is concluded that an hematocrit of approximately
20% provides the optimal combination of blood flow and oxygen-carrying
capacity while maintaining physiological perfusion pressures, e.g., 10
mmHg.
