Contractile apparatus in aortic endothelium of hypertensive rat.

One week after hypertension was produced in male Wistar rats (150 g body weight) by a complete aortic ligature placed between renal arteries, electron microscopic studies showed a striking increase of cytoplasmic microfilaments in the endothelial cells of the aortic segment above coarctation (mean blood pressure 160 mm Hg). These microfilaments measured 40-70 A in diameter and were located particularly close to the endothelial clefts. In "en face" preparation of aortic endothelial cells treated with antiactin autoantibodies (AAA) followed by antihuman IgG, the cells above the ligature of hypertensive animals were intensely fluorescent compared with those of the aortic portion below the ligature or that of controls. The fluorescence was abolished after incubating the AAA-containing sera with thrombosthenin-A, suggesting the presence of actin. There was also an increase transport of horseradish peroxidase and ferritin through the endothelial cell layer. While endothelial cells so modified may play a role in permeability regulation, they may also be related to such mechanisms as electronic coupling and synchronized contraction of aortic cells during hypertension.