Metabolism of Babesia parasites in vitro. Change in adenylate energy charge and infectivity of Babesia rodhaini-infected erythrocytes.

Studies were undertaken to investigate a possible correlation between the change, during experimental in vitro treatments, in adenylate energy charge (AEC) of B. rodhaini-infected erythrocytes and the infectivity of the parasites for mice. When the AEC and infectivity of B. rodhaini-infected erythrocytes were modified by incubation in basal salts media containing various substrates, parasite infectivity correlated significantly (r2 = 0.83, p less than 0.01) with change in AEC. However, B. rodhaini frozen with and without cryoprotectant demonstrated large changes in infectivity but relatively small changes in AEC. The final AEC values were similar to those of unfrozen organisms, although infectivity was greatly depressed. The results suggest that, when in vitro treatment changed the adenine nucleotide pool (ATP + ADP + AMP) of infected erythrocytes, change in AEC correlated with infectivity. When the adenylate pool was unchanged, no such correlation was evident. Thus, the AEC can be a useful index of parasite infectivity in some, but not necessarily in all, in vitro systems. Data on the relative utilization by B. rodhaini of various substrates, obtained when AEC and infectivity of infected erythrocytes were modified, are also reported and discussed.