Effects of estradiol and progesterone on the increased synthesis of collagen in atherosclerotic rabbit aortas.

The effects of sex hormones on atherosclerosis and collagen synthesis in blood vessels were studied in rabbits fed an atherogenic diet. Ovariectomy without hormone replacement resulted in significantly greater degree of atherosclerosis and collagen synthesis in the aortic arch when compared with the intact state. The administration of estradiol to ovariectomized rabbits resulted in a degree of atherosclerosis and collagen synthesis similar to that of intact rabbits. Ovariectomized rabbits administered progesterone on the other hand resembled the ovariectomized rabbits without hormone replacement. Specific activity of hydroxyproline in individual specimens of the arch correlated strongly with degree of atherosclerosis. An analysis of regional variation demonstrated declining values for collagen synthesis in the caudal direction along the aorta. Collagen synthesis was much higher in the portal vein as compared with the inferior vena cava. Plasma cholesterol values were higher in the ovariectomized rabbits than in the intact rabbits. Tissue deposition of cholesterol paralleled the degree of atherosclerosis.