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Abstract

Ovarian sex hormone involvement in vascular remodeling during the development of hypertension

Worthington, Jacob, BS, Baltzer, Wendy, DVM

Objective:  The purpose of this study was to determine the involvement, if any, of ovarian sex steroid hormones on vascular wall remodeling in response to hypertension.

Animals:  Male and female Sprague-Dawley rats between the ages of 12 and 15 weeks of age were used.

Procedure:  Each rate was anesthetized with an intraperitoneal ketamine/chloral hydrate injection (35/105) mg/kg).  Hypertension was induced by ligation of the abdominal aora between the right and left renal arteries with 4.0 silk in 13 intact female, 4 ovariectomized female, and 3 male rats.  The purpose in ligating the abdominal aorta at this level was to cause the left kidney to become ischemic and produce large amounts of rennin to activate the Renin-Angiotensin system to produce hypertension.  A second group of 10 intact females were used as controls, undergoing a sham surgery in which the abdominal aorta at the level of the renal arteries was exposed, but not ligated.   All rats were then euthanized 14 days post surgery by decapitation and the thoracic aorta immediately removed and fixed in formalyn.

Results:  In all three categories:  wall thickness, wall area, and wall:  lumen ratio, the intact female hypertensive rats had the largest wall size and the intact female normotensive rats had the smallest wall size.  Intact male hypertensive rats were similar to the intact female hypertensive rats.  Interestingly, ovariectomized female hypertensive rats were similar to intact female normotensive rats.

Conclusions:  There does not appear to be a great difference in vascular remodeling of aorta wall media in response to hypertension between an intact female rat and an intact male rat.  The data does suggest, however, that there is a difference between an intact female and an ovariectomized female in the vascular response to hypertension.  This would indicate a correlation between steroid sex hormones and vascular remodeling during the development of hypertension.