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Uptake of purine bases and nucleosides in African trypanosomes

Published online by Cambridge University Press:  06 April 2009

Dinah M. James  and
G. V. R. Born
Dinah M. James
Affiliation:
Department of Pharmacology, University of Cambridge, Cambridge CB2 2QD
G. V. R. Born
Affiliation:
Department of Pharmacology, University of Cambridge, Cambridge CB2 2QD
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Summary

Uptake of radioactively labelled purine bases and nucleosides by suspensions of Trypanosoma brucei and Trypanosoma congolense in bicine buffer was determined at 37 °C. With T. brucei, the rate of uptake of adenosine was much greater than that of the other compounds tested, the uptake of which decreased in the order adenine, inosine, guanosine and hypoxanthine. With T. brucei, adenosine uptake increased with concentration in a manner suggesting two mechanisms, one with high and the other with low affinity for adenosine. The uptake of adenine increased with concentration only up to about 1·5 µM while the uptake of guanosine increased little with concentration and that of inosine and hypoxanthine not at all. In both species adenosine strongly inhibited the uptake of both of the other nucleosides and of both purine bases. In T. brucei, guanosine and inosine caused small increases in adenosine uptake which was, however, inhibited by them in T. congolense. In T. brucei, each of the purine bases adenine and hypoxanthine inhibited its own uptake maximally but that of each other less effectively. Hypoxanthine was more effective than adenine in inhibiting the uptake of the nucleosides guanosine and inosine, but neither base effected marked inhibition of adenosine uptake. The uptake of adenosine by T. brucei was inhibited by dipyridamole and its analogue, compound RA–233, strongly at 100µM and slightly at 10 µM. The other dipyridamole analogues, VK–744 and VK–774, were ineffective.

Type
Research Article
Information
Parasitology , Volume 81 , Issue 2 , October 1980 , pp. 383 - 393
Copyright
Copyright © Cambridge University Press 1980

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