Plasmodium lophurae: [U- 14C]-glucose catabolism by free plasmodia and duckling host erythrocytes

Abstract

The catabolism of glucose by the avian malaria parasite Plasmodium lophurae was studied in vitro by employing the radioisotope [U- 14C]- d-glucose. Quantitatively, infected cells showed more radioisotope in soluble intermediates than did normal duck erythrocytes. Variations in the amount of 14C in these soluble products depended on the medium in which the cells were suspended; normal and Plasmodium-infected erythrocytes had considerably greater amounts of isotope in soluble intermediates when the cells were suspended in plasma rather than in buffered chick embryo Ringer's solution. P. lophurae had more radioactivity in soluble intermediates than did normal and infected cells in Ringer's solution and normal cells in plasma; however, the amount of 14C in soluble catabolites in the plasmodium was one third that recovered from infected cells in plasma. Qualitatively, the major end-products of glucose metabolism by erythrocyte-free P. lophurae and Plasmodium-infected cells in plasma were lactate and lesser amounts of succinate. The principal amino acids formed from glucose were glutamic acid, and smaller amounts of alanine and aspartic acid. Significant changes in the quality of incorporation of 14C into soluble intermediates and CO 2 were found when infected and normal cells were suspended in Ringer's solution rather than in plasma. These results are interpreted to indicate the dominant roles of glycolysis and CO 2 fixation in the metabolism of this malaria parasite.