Effects of Hypertension and Its Reversal on the Thoracic Aorta of Male and Female Rats

Abstract

Effects of hypertension and its reversal on the wall of the thoracic aorta of male and female rats were studied. Hypertension for 10 weeks caused increased diameter, wall thickness, tangential tension, wall stress, and medial area in both sexes. In addition, absolute amounts of elastin, collagen, and noncollagenous, alkali-soluble protein were significantly increased in the walls of all hypertensive vessels. Associated with the decrease of calculated tension and wall stress to normotensive levels after reversal of hypertension, wall thickness and medial area in males remained significantly greater than in controls and similar to the values found in hypertensive vessels, whereas in females these parameters returned fully to control levels. Absolute amounts of noncollagenous, alkali-soluble proteins did return to control levels after hypertension reversal, but elastin and collagen remained elevated in amounts similar to those in vessels with sustained hypertension; in females, this resulted in an above-normal concentration of these fibrous elements in the vessel wall. Compositional changes of the female vessel wall after reversal of hypertension were thus similar to but more clearcut and complete than those found in the male aorta. Recognition of irreversible changes in vessels subjected to hypertension may have implications for the benefits to be gained from blood pressure reduction on the progression of cardiovascular disease.