Influence of smoking on the number of circulating progenitor cells. A) CD34 + and CD34 + /CD133 + cell populations in peripheral blood measured by flow cytometry. Level of circulating CD34 + progenitor cells is significantly decreased by smoking in young healthy women. B) Endothelial progenitor cells analyzed by in vitro formation of colony forming unit (EPC-CFU) in a cell culture assay of peripheral blood mononuclear cells. Number of EPC-CFU is decreased by smoking in young healthy women. *p < 0.05 for comparison of non-smokers with smokers; values are mean ± SEM.