Malaria infection in rats with stimulated splenic red pulp: the blood flow and protective effect in normal and transplanted splenic tissue.

After splenic autotransplantation both weight and blood flow of the regenerated splenic tissue are decreased. In addition, the protective function of the transplant is less compared to that of the normal spleen. In the present study, the red pulp of normal and transplanted splenic tissue was stimulated by injections of phenylhydrazine to increase the weight, the blood flow, and the protective function. After stimulation, the weight of the normal spleen increased to 900 +/- 70 mg (control 530 +/- 20 mg) and the transplanted tissue to 240 +/- 70 mg (control 70 +/- 20 mg). This enlargement was caused by an increase in the splenic red pulp. However, the relative blood flow decreased in both the normal spleen and the transplant to 50% of the normal value. To evaluate the protective function of the stimulated splenic tissue, normal, splenectomized and transplanted rats were infected with Plasmodium berghei. Despite the dramatic increase in the red pulp, neither the normal nor the transplanted animals showed a survival rate superior to that of the splenectomized animals. The mass of splenic tissue obviously does not correlate with the protective effect of the spleen in parasitic infections.