Mitochondrial proliferation in endothelium. Observations on umbilical arteries from newborn children of smoking mothers.

Umbilical arteries from 52 women, 22 heavy smokers (more than 10 cigarettes per day) and 30 non-smokers were studied by transmission electron microscopy. An increased number of mitochondrial profiles was observed in many endothelial cells of smokers: chi 2 = 16.49, P less than 0.0001. The mean number of mitochondrial profiles was 23 per endothelial cell compared with 3 in non-smokers. Mitochondrial volume density (area covered by mitochondrial profiles/area cytoplasm) was measured and found to range from 0.15 to 0.62 in smokers, and 0.01 to 0.02 in non-smokers. Mitochondrial index (mitochondrial volume density/number of mitochondrial profiles) was calculated and found to be 0.008-0.060, mean value 0.018, in smokers, and 0.003-0.008, mean value 0.006, in non-smokers. Thus, in smokers a larger area of the endothelial cell cytoplasm was often occupied by mitochondria, a greater number of mitochondrial profiles was found, but the mean size of the mitochondria (profiles) was only slightly increased.