Metabolism of Babesia parasites in vitro. Glucose and energy-metabolism and survival of Babesia rodhaini in a basal medium with and without adenosine.

During in vitro incubation in Krebs Ringer phosphate (KRP) medium, rat erythrocytes about 20% parasitized with B. rodhaini used two to four times as much glucose as unparasitized erythrocytes. However, the AtP concentration and the ATP production of parasitized erythrocytes decreased. For example, before incubation the ATP concentration in parasitized erythrocytes was significantly higher thant unparasitized erythrocytes, but following 0.5 h incubation it was reduced to about the same as in unparasitized erythrocytes. Addition of 5 X 10(-3) M adenosine to the basal medium increased the ATP production and the adenylate energy charge of parasitized erythrocytes. Infectivity tests in susceptible mice showed that, despite these seemingly favourable changes in energy metabolism, adenosine had no detectable effect on the survival of B. rodhaini. Absence of infectivity showed the inability of KRP medium to support B. rodhaini for 22 h in vitro with or without adenosine. Adenosine also greatly decreased the glucose uptake by parasitized erythrocytes, apparently by competitive inhibition, since lactate production was unchanged.