AJP - Gastrointestinal and Liver Physiology, Vol 251, Issue 1 34-G39, Copyright © 1986 by American Physiological Society
Adenosine export from the liver: oxygen dependency
S. T. Arnold and R. L. Cysyk
The liver is believed to be an important regulator of purine concentrations
in the circulation. It has been an accepted notion that the liver exports
the riboside adenosine to the circulation for use by other tissues. This
phenomenon was reexamined using an artificial oxygen carrier to perfuse the
isolated rat liver and high-performance liquid chromatography (HPLC) to
analyze the purine content. It was found that perfusion with
Krebs-Ringer-bicarbonate at a physiological flow rate as had been used by
previous investigators results in a mildly hypoxic preparation, and it is
this hypoxia that results in the export of adenosine. In a liver perfused
with Fluosol-43, little (less than 0.05 microM) or no adenosine was
released. However, if the oxygen content of Fluosol-43 was decreased, the
liver could be induced to release adenosine at 1.0 microM levels. In
addition, the liver was found to release adenine under control conditions;
thus it is this purine base that is likely to be the important purine
released by the liver for extrahepatic salvage, not adenosine as previously
thought.
