Mitotic delay in peripheral blood lymphocytes and fibroblast cultures obtained from a child with Down's syndrome and from a healthy child.

Mitotic delay (MD) often occurs in cells of donors exposed in vivo to genotoxic agents. To investigate individual sensitivity with genetic background, author measured the 3-methyl-cholanthrene (MC)-induced MD in cultured human skin fibroblasts (FBs) and in peripheral blood lymphocytes (PBLs) obtained from a 4-year-old patient with Down's disease. Samples from a 10-year-old healthy subject served as controls. Skin samples were obtained during surgical intervention. The induced MD was calculated from the mitotic index (MI) which was expressed in per cent of the control; at various times up to 18 h after treatment. Cells were treated with 10(-7), 10(-6) and 10(-5) M MC (with S-9 liver homogenate). At passage 10, the average MI (+/- SE) was 8.32 +/- 0.43%, and 7.85 +/- 0.64% for the healthy and for the Down's FBs, respectively; and it was 4.89 +/- 0.59%, and 4.92 +/- 0.72% for the healthy and for the Down's PBLs, respectively. MD was characterized as 50% MI of control (MD50). The MD50 values were the most expressed when cells were treated with 10(-5) M MC. No difference was found in MD of healthy and Down's fibroblasts. For Down's lymphocytes, on the other hand, MD was approximately 30% longer than for healthy cells. This result agrees well the reported increased SCE and decreased DNA-repair data obtained in PBL of Down patients.