The absorption of prothidium by Trypanosoma rhodesiense.

When rats, heavily infected with Trypanosoma rhodesiense, were injected with Prothidium and killed 1 to 5 hours later, measurable amounts of the drug could be extracted from the parasites: a million trypanosomes have been shown to absorb 0.01 to 0.06 mug. of Prothidium in vivo. When viewed with the fluorescence microscope, treated trypanosomes appeared to concentrate Prothidium particularly in the blepharoplast and other cytoplasmic granules. Prothidium was absorbed by trypanosomes in vitro in less than 30 min. When equilibrium had been reached the concentration of the drug inside the trypanosome was approximately 400 times the concentration outside, in the range of concentrations studied.