Intracellular diminazene aceturate content and adenosine incorporation in diminazene aceturate-resistant Babesia gibsoni isolate in vitro.

The mechanism of the development of diminazene aceturate (DA) resistance in Babesia gibsoni is still unknown even though DA-resistant B. gibsoni isolate was previously developed in vitro. To clarify the mechanisms of DA-resistance in B. gibsoni, we initially examined the intracellular DA content in the DA-resistant isolate using high-performance liquid chromatography, and compared it with that in the wild-type. As a result, the intracellular DA content in the DA-resistant isolate was significantly lower than that in the wild-type, suggesting that the decreased DA content may contribute to DA-resistance. Additionally, the glucose consumption of the DA-resistant isolate was significantly higher than that of the wild-type, indicating that a large amount of glucose is utilized to maintain DA-resistance. It is possible that a large amount of energy is utilized to maintain the mechanisms of DA-resistance. It was reported that as the structure of DA is similar with that of adenosine, DA may be taken up by the P2 transporter, which contributes to the uptake of adenosine, in Trypanosoma brucei brucei, and that the uptake of adenosine is decreased in DA-resistant T. brucei brucei. In the present study, the adenosine incorporation in the DA-resistant B. gibsoni isolate was higher than in the wild-type. Moreover, the adenosine incorporation in the wild-type was not inhibited by the presence of DA. These results suggest that adenosine transport in B. gibsoni is not affected by DA and may not mediate DA-resistance. To clarify the mechanism of the development of DA resistance in B. gibsoni, we should investigate the cause of the decreased DA content in the DA-resistant isolate in the future.