Dexamethasone suppresses the generation of phenylhydrazine-induced anemia in the rat.

The immunoactive steroid dexamethasone (DXM) was administered to rats injected with a dose of phenylhydrazine (PHZ) known to induce anemia. PHZ treatment alone resulted in a hemolytic anemia that was most pronounced on Days 1-7 after injection. This anemia was accompanied by a leukocytosis that was greatest on Days 2-7 following PHZ treatment. Lymphocytes accounted for greater than 75% of this incremental increase. In contrast, rats treated with PHZ as well as with DXM displayed erythrocyte counts and hematocrits within the normal range. Although the reticulocyte counts of these rats were higher than those of controls, they were significantly lower than those of animals receiving PHZ alone. In addition, DXM suppressed the leukocytosis and splenomegaly resulting from PHZ administration and inhibited the rise in plasma IgG titers induced by PHZ exposure. DXM also altered the ratio of peripheral blood T and B lymphocytes of PHZ-treated rats. DXM suppression of PHZ-induced anemia is further confirmation that this anemia is associated with immune activation.