Vascular injury has been suggested as a possible mechanism for late radiation damage to various organs. However, little is known about the radiobiology of cells of the blood vessel wall. We have studied the radiation survival properties of exponentially growing cultures of vascular smooth muscle cells. Medical smooth muscle cells were obtained from the thoracic aortas of 3- to 4-month-old Sprague-Dawley rats and were propagated in cell culture using standard techniques. Cultures from different strains were irradiated using137 Cs γ radiation after varying periods in culture. Clonogenic survival was measured via colony formation assays. The mean D0 for seven survival curves utilizing four different strains of cells was 147 ± 22 rad (range 117-176) and the mean extrapolation number (corrected for colony multiplicity) was 3.7 ± 2.7 (range 1.1-9.5). Split dose survival assays demonstrated repair of sublethal radiation damage within the first 4 hr with recovery factors approximately equal to the extrapolation number. We conclude that rat aortic medial smooth muscle cells show moderate radiosensitivity similar to that measured in vitro for a variety of mammalian cell lines and in vivo for epithelial tissues in rodents.

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