Fatty acid uptake by bloodstream forms of Trypanosoma brucei and other species of the kinetoplastida.

1. Trypanosoma brucei and other species of the Kinetoplastida readily take up fatty acids from a simple incubation medium. This suggests that they at least partially satisfy their nutritional requirements for fatty acids from an exogenous source. 2. Uptake of fatty acids in T. brucei follows a biphasic time course, consisting of an initial rapid phase, thought to represent surface binding, followed by a slower accumulation phase. 3. Culture forms of T. brucei take up more than 10 times as much fatty acid during the rapid initial phase than do bloodstream forms, suggesting the presence of a greater number of fatty acid binding sites in the plasma membranes of the culture forms when compared to the bllodstream forms. 4. The uptake process is reversible. Measurements of the release of a preloaded fatty acid from bloodstream forms of T. brucei, in the presence and in the absence of albumin, provides some support for the hypothesis that fatty acid uptake and release is mediated by a direct interaction of free albumin and fatty acid-albumin complex with the cell surface.