THE INFLUENCE OF ACUTE STERILE INFLAMMATION ON ERYTHROPOIESIS IN RATS

Many different cell types, coordinated by proinflammatory mediators, t ake part in the acute inflammatory reaction, but there is a lack of ev idence regarding the role of erythroid cells in such conditions. In th is study, changes in bone marrow, splenic, and peripheral blood erythr oid cells and in erythropoietin (Epo) blood levels were investigated u p to 72 hours after polyvinylpyrrolidone (PVP)-induced sterile inflamm ation in male Wistar rats (two intraperitoneal injections of 15 mL 3.5 % PVP at 18-hour intervals). Transient changes within progenitor eryth roid cells were observed in the bone marrow. Significant increases in the number of splenic immature erythroid progenitors (BFU-E) 6 hours a nd mature erythroid progenitors (CFU-E), erythroblasts, and orthochrom atic erythroblasts 48 and 72 hours after the induction of inflammation pointed to stimulated splenic erythropoiesis. This was confirmed by s emiquantitative assessment of splenic smears, which demonstrated expan sion of erythroid cells at hours 48 and 72. The changes observed in th e bone marrow and spleen indicated that during acute inflammation eryt hropoiesis was stimulated and that the spleens of PVP-treated rats wer e favorable to erythroid development. The significant increase in the percentage of peripheral blood reticulocytes 48 and 72 hours after PVP -induced inflammation provided evidence that effective erythropoiesis occurred. In spite of the stimulated erythropoiesis, serum levels of E po remained unchanged, implying that other non-Epo regulatory molecule s may be responsible for erythroid cellular changes.