Aortic endothelial and subendothelial cells in experimental hypertension and aging

The endothelial and subendothelial cellular changes occurring as a result of hypertension and aging were characterized in deoxycorticosterone/salt-treated (D/S), spontaneously hypertensive (SHR), and Wistar-Kyoto (WKY) rats. An increase in the number of subendothelial cells occurred with both hypertension and aging and was most dramatic with D/S hypertension. Many of the cells found in the widened subendothelium showed morphological characteristics of mononuclear cells (both macrophages and lymphocytes), and of smooth muscle cells. Normalization of blood pressure by withdrawal of D/S and maintenance of rats on a low salt diet reversed the number of subendothelial cells to levels of control animals of comparable age. Significant alterations were seen in the aortic endothelial cells of D/S animals. Within 2 to 4 weeks of D/S administration, the endothelial cells doubled in number and often assumed bizarre shapes with nuclear folding and bulging toward the lumen. Some similar abnormalities in endothelial cell shape and appearance occurred with increasing age in the SHR and control WKY, although the number of endothelial cells increased only slightly in these groups. These results suggest that profound cellular changes in the aortic intima occur with an increase in blood pressure. These changes are pronounced in the D/S model of hypertension, while virtually absent in SHR. Comparable alterations also may be seen in aged normotensive animals, but to a lesser extent and with slower progression.