DETECTION OF PYRIMETHAMINE-INDUCED DNA-DAMAGE IN MOUSE EMBRYO AND MATERNAL ORGANS BY THE MODIFIED ALKALINE SINGLE-CELL GEL-ELECTROPHORESIS ASSAY

We studied the embryonic and maternal genotoxicity of pyrimethamine (P YR), a potent teratogen and folate antagonist, using alkaline single c ell gel electrophoresis (SCG, or Comet) assay as modified by us (we us ed isolated nuclei instead of isolated cells). ICR mice were treated o n the 13th day of pregnancy with a single oral dose of 50 mg PYR/kg. S ix maternal organs (liver, kidney, lung, brain, spleen, bone marrow), maternal and fetal placentas, and two embryos were taken 6 and 16 h af ter treatment; the embryos were divided into head and body portions. E ach sample was minced, homogenized gently, and centrifugred. The nucle i from the precipitates were used. PYR induced DNA damage in all mater nal organs except spleen and bone marrow 6 h after administration. The DNA damage in all the affected organs was less at 16 h than at 6 h, a nd that of the kidney and brain returned to control level at 16 h. PYR also induced DNA damage in maternal and fetal placentas and embryos t hat was detected at 6 and 16 h, with greater damage at 6 h. Go-treatme nt of folinic acid calcium salt (FNA, 10 mg/kg ip), a reduced active f olate form, prevented the PYR-induced DNA damage in all target tissues examined 6 h after treatment. These data indicate that the observed e mbryonic and maternal DNA damage caused by PYR may be related to folat e deficiency, and that the modified alkaline SCG assay can be used to predict fetal/embryonic genotoxicity in vivo, in addition to the organ -specific maternal genotoxicity. (C) 1998 Elsevier Science B.V. All ri ghts reserved.