Changes in stem cell compartments in mice after hydroxyurea.

Hydroxyurea injection kills only approximately 10% of CFUs which are in the S phase of the cell cycle. In mice given a single injection of hydroxyurea CFUs in the femur decreased only about 50% in 2--4 days after hydroxyurea, and then started to return to normal levels with an overshoot evident after the eighth day after hydroxyurea. CFUs in spleens of mice given a single injection of hydroxyurea show an evident overshoot as early as 3 days after the drug, reaching levels which are about 300% of normal. CFUs from blood disappear rapidly, but equally rapidly return to normal values followed by a significant overshoot. The radioresistance of mice increased up to 4 days after hydroxyurea.