Hydroxyurea: effect on growth, structure, and [3H]thymidine uptake of Trypanosoma brucei procyclic culture forms.

Hydroxyurea (HU) in concentrations above 50 micrograms/ml reversibly inhibited cell division of Trypanosoma brucei brucei stock STIB 336 procyclic culture forms, but not growth of individual cells. The volume of the nucleus and of the cytoplasm increased in the presence of the drug as did the percentage of cells with 2 kinetoplasts. Electron microscopy revealed that the nuclear membrane was extended forming protrusions which surrounded areas of the cytoplasm. Replication of the kinetoplast DNA did not seem to be affected by HU. The uptake of [3H]thymidine increased in the presence of 25 micrograms/ml HU 3-fold compared to control cells. The nuclear volume and the dry weight of the culture forms increased proportionally to the amount of label incorporated.