Effect of vincristine on sister chromatid exchanges of normal human lymphocytes.

In vitro analysis of the mitosis from 3-day lymphocyte cultures from two normal males and two normal females treated with bromodeoxyuridine and stained with acridine orange after addition of vincristine during different times demonstrated that vincristine inhibits the progression of the second division. When the second division progressed, the number of sister chromatid exchanges was significantly decreased. Vincristine could act by inhibiting the copying of DNA. A dosage effect is demonstrated when vincristine is added to the cultures during the first 24 hr.