Hydralazine treatment significantly lowered arterial pressure but did not alter the enhanced contraction to phenylephrine or enhanced relaxation to acetylcholine in coronary arteries from SHR.
Does hydralazine treatment alter coronary vascular responsiveness in spontaneously hypertensive rats?
In 12-14 week-old spontaneously hypertensive rats, coronary arteries exhibit enhanced alpha-adrenoceptor-mediated contraction and preserved endothelium-dependent relaxation, which are not reversed by lowering arterial pressure with hydralazine.
Coronary artery disease often occurs in patients with hypertension. The present study was designed to evaluate coronary vascular function in isolated coronary arteries of spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats and to determine the effect of antihypertensive treatment on coronary vascular responsiveness. Male SHR and WKY rats (12 to 14 weeks old) were divided into control and hydralazine-treated (120 mg/L drinking water for 10 days) groups. After 10 days, arterial pressure and heart rate were recorded while rats were conscious and unrestrained. Left ventricular coronary arteries (200 to 300 microns diameter) were isolated and intraluminal diameter was continuously recorded while vessels were maintained at a constant intraluminal pressure of 40 mm Hg. Relaxation of coronary arteries to both acetylcholine and nitroprusside was slightly, but significantly, enhanced in vessels from SHR compared to WKY rats. The enhanced relaxation was a specific effect, since isoproterenol induced similar relaxation in coronary arteries from SHR and WKY rats. Contraction to phenylephrine, but not endothelin-1, was augmented in coronary arteries from SHR compared to WKY rats. Treatment with hydralazine significantly lowered arterial pressure in SHR and WKY rats, but did not alter the enhanced contraction to phenylephrine or the enhanced relaxation to acetylcholine and nitroprusside in coronary arteris from SHR. These results indicate that coronary arteries of 12 to 14 week-old SHR do not have impaired endothelium-dependent relaxation, but to exhibit enhanced alpha-adrenoceptor-mediated contraction that is not reduced by lowering arterial pressure.
Leslie C. Fuchs (Wed,) conducted a other in Hypertension. Hydralazine vs. Control was evaluated on Coronary vascular responsiveness (relaxation to acetylcholine and nitroprusside, contraction to phenylephrine). Hydralazine treatment significantly lowered arterial pressure but did not alter the enhanced contraction to phenylephrine or enhanced relaxation to acetylcholine in coronary arteries from SHR.