Primaquine-lnduced Hemolytic Anemia: Role of Splenic Macrophages in the Fate of 5-Hydroxyprimaquine-Treated Rat Erythrocytes

摘要

Primaquine-induced hemolytic anemia is known to result from premature sequestration of damaged (but intact) erythrocytes by the spleen.We have shown previously that a phenolic metabolite,5-hydroxyprimaquine (5-HPQ),is a direct-acting hemolytic agent in rats,suggesting that 5-HPQ is a mediator of the hemolytic response to primaquine.To investigate the fate of erythrocytes in vivo after in vitro exposure to 5-HPQ,rat ~(51)Cr-labeled erythrocytes were incubated with hemolytic concentrations of 5-HPQ and then readministered intravenously to rats.The time course of loss of radioactivity from blood and uptake into the spleen and liver was measured.In rats given 5-HPQ-treated erythrocytes,an increased rate of removal of radioactivity from the circulation was observed as compared with the vehicle control.The loss of blood radioactivity was accompanied by a corresponding increase in radioactivity appearing in the spleen but not in the liver.When rats were pretreated with clodronate-loaded liposomes to deplete splenic macrophages,there was a decreased rate of removal of radioactivity from the circulation and a markedly diminished uptake into the spleen.A role for phagocytic removal of 5-HPQ-treated red cells was confirmed in vitro using the J774A.1 macrophage cell line.Furthermore,depletion of red cell GSH with diethyl maleate significantly enhanced in vitro phagocytosis of 5-HPQ-treated red cells.The data indicate that splenic macrophages are responsible for removing 5-HPQ-treated red cells and support the postulate that this metabolite is a contributor to the hemolytic anemia induced after administration of the parent compound.