Altered intracellular polyamines in bloodstream form Trypanosoma brucei brucei: transformation to procyclic trypomastigotes.

A monomorphic strain of Trypanosoma brucei brucei (EATRO 110) was cultured as long slender bloodstream forms in vitro for 24 h with 100 microM Eflornithine HCl. This resulted in depletion of intracellular putrescine, a greater than 50% decrease in spermidine, and a cessation of cell division. These Eflornithine treated trypanosomes were stimulated to synchronously transform to procyclic trypomastigotes by transfer into SDM-79 medium containing the citric acid cycle intermediates citrate and cis-aconitate (CCA). Within 48 h morphological transformation was complete and occurred without any increase in cell numbers. The coadministration of 100 microM putrescine with Eflornithine prevented the depletion of putrescine and abrogated the cytostatic effect of Eflornithine alone, but did not prevent the transformation to procyclic trypomastigotes. Eflornithine-induced short stumpy form trypanosomes resulting from 4 days of culture with 100 microM Eflornithine did not transform to procyclic trypomastigotes in SDM-79 medium unless it contained CCA. We conclude that the high concentration of CCA can trigger transformation in all morphological types of bloodstream form trypanosomes, regardless of their threshold of sensitivity for the stimulus. Furthermore, the CCA-stimulated transformation is not dependent on putrescine and can occur independently of cell division.