ERYTHROPOIETIN MESSENGER RNA EXPRESSION IN THE KIDNEYS OF MICE WITH ACUTE ANEMIA

Localization of erythropoietin messenger RNA was studied by an in situ hybridization procedure using anti-sense oligonucleotide probes of murine erythropoietin in the kidneys of mice with acute anemia. Acute anemia was induced by depletion of blood. Five hundred microliters of blood were withdrawn form orbital plexus 6, 24, and 30 hours before necropsy. Animals were sacrificed 6 hours after the last bleeding. Erythropoietin levels in the plasma, renal cortex, and medulla were 797.0mU/ml, 216.7, and 11.3mU/g protein, respectively, and these values were 50, 16, and 4.5times higher than those in the untreated control mice. Silver grains indicating erythropoietin messenger RNA expression were observed in the interstitial cells of the renal cortex and outer stripe of the outer medulla in the mice with acute anemia, but not in the renal tubules or glomeruli. Silver grains were not detected in the kidneys of the untreated control mice. From these results, it was concluded that the main area of erythropoietin synthesis in the kidneys was the interstitial cells in the renal cortex and outer stripe ofthe outer medulla in the mice with acute anemia.