Proliferation of arterial smooth muscle: glucocorticoid effect

Tritiated thymidine radioautography was employed to study the effect of glucocorticoids on smooth muscle proliferation in rabbit arteries. In the aorta and pulmonary artery of rabbits with cholesterol atherolsclerosis, labelled cell counts showed that these steroids decrease the deoxyribonucleic acid synthesis in the intimal plaques. The inhibitory effect on thymidine uptake was found to be dose dependent and closely related to the antiinflammatory potency of the steroid tested. In another set of experiments the smooth muscle proliferation occurring in the rabbit carotid artery after disendothelization was studied. In these normolipemic animals the inhibition of DNA synthesis was particularly evident in the medial smooth muscle cell; concomitantly, in steroid-treated animals the myointimal thickening in the denuded area was less prominent. It is concluded that very likely the glucocorticoid effect on the artery is due to a direct interaction of the steroid with smooth muscle cells.