The hemin effect on protein synthesis of human granulocytes, lymphocytes and platelets was examined. Hemin added to culture media without serum caused a dose-dependent inhibition of protein synthesis in all three cell types. A cell-specific enhancement of protein-synthesizing capability was observed in 24-hour cultures in the presence of hemin and serum. A marked increase of protein synthesis was found in granulocytes, unchanged in lymphocytes and decreased in platelets. Lymphocytes from patients with chronic lymphatic leukemia (CLL) were moderately inhibited by hemin when incubated in media containing serum, the effect being more pronounced in the presence of freshly dissolved doses of hemin. Addition of protophyrin IX to cell cultures resulted in a marked suppression of protein synthesis by the three cell types, in all experiments. These results confirm the importance of serum proteins in preventing the inhibitory effects of free hemin and protoporphyrin IX on blood cell protein synthesis. On the other hand, they show a cell-specific enhancement of the protein-synthesizing capacity mediated by hemin.
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