RESUMO
The results of the present study reveal an early increase in activity levels of creatine kinase and lactate dehydrogenase in the plasma of mice infected with Trypanosoma cruzi strains K-1, X-1, and Tulahuen as compared with uninfected control mice. An increase in creatine kinase activity was detected earlier in K-1- and X-1-infected mice than in Tulahuen-infected mice. Moreover, an increase in lactate dehydrogenase activity occurred at 1.5 days after infection with the X-1 and Tulahuen strains and at 3.5 days after infection with the K-1 strain. Generally, the highest activity levels were found in the plasma of mice infected with the most virulent and lethal Tulahuen strain as compared with the less virulent and nonlethal K-1 and X-1 strains. A significant decrease in creatine kinase levels occurred later in the tissues than in the plasma of K-1- and X-1-infected mice but did not vary significantly in any of the tissues from Tulahuen-infected mice. Similarly, the specific activity of lactate dehydrogenase in tissues from K-1- and X-1-infected mice dropped at a later stage than did the activity in plasma, but infection with the Tulahuen strain caused an earlier reduction in the activity of lactate dehydrogenase in the heart and skeletal muscle. The activity levels of both enzymes in plasma and tissues showed a linearly negative and statistically significant correlation. The present study reveals that levels of creatine kinase and lactate dehydrogenase activity in plasma could be early indicators of and suitable tools for monitoring of the infectivity of these strains of T. cruzi and might reflect their inherent histotropism during experimentally acute Chagas' disease.