Recovery of an erythropoietin inducing factor from the regenerating rat liver.

The perfusion of livers of partially hepatectomized (H mean) rats lends support to earlier findings that the regenerating rat liver is the source of an erythropoietin-inducing hepatic factor (Ep-IHF) which stimulates hepatic production of extrarenal erythropoietin (Ep). Blood plasma was collected from perfused livers of rats that were partially hepatectomized (H mean) 48 to 72 hrs prior to perfusion with whole blood from normal rats. This plasma, when injected into normal rats which were nephrectomized (N mean) and rendered hypoxic 18 hrs after injection, evoked a significant increase in Ep values when compared to blood plasma collected from perfused livers of normal rats. Ep values were significantly higher when regenerating livers were perfused with blood collected from nephrectomized (N mean) rats than when such livers were perfused with blood of normal rats. The highest Ep values resulting from the liver perfusions were obtained when the liver donor and blood donor rats were both H mean and N mean. The results demonstrate that the liver is the principal source of an Ep-inducing factor since perfusion of the liver eliminated other potential tissue sources of activity in the rat. This was achieved by perfusing the livers directly through the portal vein and collecting the perfusate from the hepatic vein, thereby eliminating potential contributions from organs draining into other parts of the systemic circulation. In addition, it was shown that the kidney inhibits the activity and/or production of the Ep-IHF which is evoked by H mean.