Favism is an acute anemic crisis that can occur in susceptible individuals who ingest fava beans. The fava bean
pyrimidine aglycone
divicine has been identified as a hemotoxic constituent; however, its mechanism of toxicity remains unknown. We have shown recently that
divicine can induce a favic-like response in rats and that
divicine is directly toxic to rat red cells. In the present study, we have examined the effect of hemotoxic concentrations of
divicine on rat erythrocyte sulfhydryl status,
hexose monophosphate (HMP) shunt activity, morphology, and membrane skeletal
proteins. In vitro exposure of rat red cells to
divicine markedly stimulated HMP shunt activity and resulted in depletion of
reduced glutathione with concomitant formation of
glutathione-
protein mixed-
disulfides. Examination of
divicine-treated red cells by scanning electron microscopy revealed transformation of the cells to an extreme echinocytic morphology. SDS-PAGE and immunoblotting analysis of the membrane skeletal
proteins indicated that hemotoxicity was associated with the apparent loss of skeletal
protein bands 2.1, 3, and 4.2, and the appearance of membrane-bound
hemoglobin. Treatment of
divicine-damaged red cells with
dithiothreitol reversed the
protein changes, which indicated that the observed alterations were due primarily to the formation of
disulfide-linked
hemoglobin-skeletal
protein adducts. The data suggest that oxidative modification of
hemoglobin and membrane skeletal
proteins by
divicine may be key events in the mechanism underlying
favism.