METABOLIC STRESS IN NORMAL AND ABNORMAL HUMAN RED CELLS

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In human red cells, stress occurs when the normally slow moving metabolic machinery of the red cell is forced to accelerate beyond its normal rate. Metabolic stress is found in red cells parasitized by malaria and in some pathological states such as in myeloproliferative diseases (MPD). Glucose-6-phosphate dehydrogenase deficient red cells (G6PD-) are especially vulnerable to stress because they cannot augment pentose shunt metabolism. This study intends to investigate the salient features of normal and abnormal human red cells infected in vitro with falciparum malaria. In particular, the mechanism whereby G6PD- cells inhibit the growth of malaria will be studied. Two hypotheses will be tested: A. Oxidative stress in malaria infected cells interacts with the enzyme deficiency to inhibit growth. B. G6PD- cells cannot produce enough ribose phosphate for nucleotide needs of the growing parasites. These two hypotheses are not mutually exclusive. Methodology will include culture of malaria in vitro, assays for susceptibility to membrane lipid peroxidation, incorporation of labelled precursors into nucleotides, and a study of the growth of malaria in relation to the supply of phosphoribosylpyrophosphate (PRPP) - a key metabolite of the pentose pathway. MPD red cells are characterized by high concentrations of reduced glutathione (GSH) and increased glycolytic enzyme activity and in some ways resemble immature red cells or cord cells. They also have an increased susceptibility to membrane lipid peroxidation, which is linked somehow to the high GSH content. The nature of this relationship will be explored by studying the tendency of crude and purified red cell lysates to oxidize hemoglobin and elaborate active forms of 02. The effect of these lysates on sealed red cell ghosts and liposomes will also be studied. GSH may function as a pro-oxidant as well as an anti-oxidant under some conditions. Whether or not pro-oxidant conditions occur in MPD red cells remains to be determined. The requirement of PRPP synthetase for GSH in intact red cells will also be studied as will GSH synthesis and degradation rates. Manipulations of GHS may alter the course of MPD, reduce transfusion needs, inprove blood storage, enhance knowledge.