Autoradiographic studies of the smooth muscle cells in human arteries.

We have studied the kinetics of smooth muscle cell growth in the tunica media of human arteries obtained from 12 patients affected by obstructive vascular disease, and one case operated because of a trauma. The studies were carried out on arterial samples by autoradiography after in vitro labelling with 3H-thymidine. Different patterns of radioactive nucleotide uptake were detected. On nine elastic and muscular arteries without pathological changes it was demonstrated that the turnover of smooth muscle cells in human medias was very low, and similar to that found in experimental animals. The medias under atherosclerotic plaques showed variable levels of tritium uptake. Although the number of cases surveyed was limited, a possible explanation is that the different levels of uptake could depend on the different evolutive stages of the atherosclerotic process. It cannot, however, be excluded that the proliferative activity of the smooth muscle cells may be related to focal damages of the tunica media.