Hydroxyurea-induced synchrony of DNA replication in the Kinetoplastida.

We have developed a reliable and reproducible method to induce synchrony of the DNA synthetic cycle in the Kinetoplastida. The method involves treatment of cultures with 20 mM hydroxyurea (HU) and fetal bovine serum. Both stationary-phase and exponential-phase cultures can be synchronized. However, in the case of exponential-phase cultures the population doubling time and rate of DNA synthesis of the population influenced the time of exposure to HU. The treatment of kinetoplastids with 20 mM HU did not adversely affect the cells as judged by oxygen consumption, RNA, and protein content. We postulate that the requirement for high HU levels, which would be toxic to vertebrate cells, may be due to a lower affinity of kinetoplastid ribonucleotide reductase, the target enzyme for HU. Some of the kinetoplastids are pathogens of man and his food chain. Consequently, the development of a reliable technique for synchronization of the kinetoplastids should not only permit a detailed analysis of their cellular and molecular biology but provide a means to collect and characterize biochemical and immunochemical substances relevant to the infectious process.