Detection of fragile sites induced by pyrimethamine.

In this study, the effect of pyrimethamine in inducing expression of fragile sites in human peripheral blood lymphocyte cultures is investigated. In vitro lymphocyte cultures of 15 healthy individuals were treated with 0.02 mg/ml of pyrimethamine for 48 and 72 hr. One culture was used as control. The number of cells showing chromosomal aberration increases significantly in the cultures after 48 and 72 hr in comparison to the control group (P < 0.001). Localization of fragile sites was determined by the G-banding method and light microscopy. As a result, five folic acid-sensitive fragile sites (1p32, 1q32, 3p14, 6p22, 14q24) were detected.