The Effects of Estrogen on Relaxation Rates in Smooth Muscle Rat Caudal Artery

Studies show that menopausal women are more at risk for heart problems, possibly due to diminishing production of reproductive hormones.  Heart problems arise from alteration in cardiovascular muscle functions. If these hormones upkeep cardiovascular health by altering protein functions that regulate smooth muscle and artery relaxation then we should note a difference in muscle output when hormone amounts differ. This project studies the effect of varying levels of naturally produced reproductive hormones on relaxation rates in rat caudal arteries. Retired breeding rats are used as models because of available literature and they are known to experience a peak and decline in natural progesterone and estrogen levels every four days.  Experiments were performed on tissue collected from rats during various phases of the cycle.  Changes in cell structure visualized on PAP smears were used to indicate hormone levels. Rat caudal artery, isometrically held, was electrically stimulated in muscle bath kept at physiological conditions. Arterial contraction and relaxation rates were recorded using data acquisition software. Relaxation curves matched a double exponential decay curve, and were analyzed by fitting results to an equation using JSIM modeling software. When comparing the main and slow relaxation rate constant component during the Estrogen and Progesterone phase, the arterial muscle had the same distribution across both hormones. There was no statistical significance in the physiologically prepared experiments.  Experiments are being repeated to mimic menopause and use ovariectomized female rats rescued with known estrogen amounts.