Inosine from liver as a possible energy source for pig red blood cells

Adult pig red blood cells are unable to metabolize glucose due to a membrane permeability barrier to glucose developed shortly after birth. $\text{In}$$\text{vitro}$, pig red cells incubated in their own plasma are unable to maintain normal ATP levels, thus the question has been raised as to the nature of the metabolic energy source. We have suggested that organs, such as the liver, might supply low levels of substrate to the red cells as they transit through the organ. In this paper, evidence is presented to show that perfused pig livers supply a metabolic substrate used by pig red cells. This substrate has been tentatively identified as inosine.