Information on morphological and functional effects of anemia in kidne
y is scarce, although this organ plays a major role in erythropoietin
production, which is strongly stimulated in anemia. We undertook a mor
phological study of kidneys of anemic rats. Anemia was induced by X-ir
radiation and subsequent injection of a hemolytic drug. The most strik
ing effects of anemia on renal morphology were damages in the proximal
tubule and a volume increase of the peritubular space. These effects
were evident only in the cortical labyrinth. Morphometry showed that t
he enlargement of the peritubular space reflected an increase of the v
olumes of both capillaries and interstitium. The structural changes in
the cortical interstitium were associated with increased activity of
the ecto-5'-nucleotidase in the fibroblasts. We suggest that hypoxia a
ccounts for most of the observed alterations. The hypoxic proximal tub
ule might release the nucleotide AMP, which would be hydrolyzed to ade
nosine by the ecto-5'-nucleotidase in the interstitium. Adenosine has
been reported to trigger the synthesis of erythropoietin and the growt
h of blood capillaries.