HEART FOF1-ATPASE CHANGES DURING THE ACUTE-PHASE OF TRYPANOSOMA-CRUZIINFECTION IN RATS

The kinetic properties of ATP hydrolysis and synthesis by FoF1-ATPase of heart mitochondria were evaluated during the acute phase of T. cruz i infection in rats. Mitochondria and submitochondrial particles were isolated 7 days (early stage) and 25 days (late stage) following infec tion of rats with 2 x 10(5) trypomastigote forms of the Y strain of T. cruzi. The kinetic properties for ATP hydrolysis were altered for the early but not the late stage, showing a changed pH profile, increased K-0.5 values, and a decreased total V-max. The Arrhenius' plot for me mbrane-associated enzyme showed a higher transition temperature with a lower value for the activation energy in body temperature. For the Tr iton X-100 - solubilized enzyme, the plot was similar to the control. A decrease in the efficiency of ADP phosphorylation by mitochondria, m easured by the firefly-luciferase luminescence, was observed only duri ng the late stage and appeared to be correlated with a decrease in the affinity of the FoF1-ATPase for ADP. It is proposed that in the early stage, during the acute phase of T. cruzi infection in rats, heart Fo F1-ATPase undergoes a membrane-dependent conformational change in orde r to maintain the phosphorylation potential of mitochondria, which wou ld compensate for the uncoupling of mitochondrial function. Also, duri ng both the early and late stages, the enzyme seems to be under the re gulation of the endogenous inhibitor protein for the preservation of c ellular ATP levels.