Significant Vasodilator Effect Research Articles

Assessment of coronary vasomotion by intracoronary ultrasound

This study was performed to evaluate the accuracy of intravascular ultrasound for the assessment of coronary artery vasomotion and endothelial function in patients with atherosclerosis. Twenty patients with luminal irregularities on the coronary angiogram and a high cholesterol level (287 +/- 19 mg/dl) (group 1) and six patients with angiographically smooth arteries and a minimally elevated cholesterol level (197 +/- 12 mg/dl) (group 2) were studied. A mechanical intravascular ultrasound probe (4.3F) was placed into the proximal segment of the coronary artery. The ultrasound images were recorded on super VHS videotape and were then digitized allowing the measurement of the lumen area and then the calculation of a mean intimal thickness index. Endothelial function was studied during sympathetic stimulation by a cold pressor test and, after increasing coronary blood flow, by intracoronary papaverine administration; a 1 mg bolus of linsidomine was then administered into the coronary artery. Patients in group 1 had a higher mean intimal thickness (1.52 +/- 0.64 mm) than those in group 2 (0.18 +/- 0.08 mm) (p < 0.001). In response to sympathetic stimulation, a vasoconstricting effect occurred in group 1 (9.5 +/- 1.3 mm2 vs 11.4 +/- 1.2 mm2 at baseline, p < 0.05), while a vasodilating action was observed in the control group (11.6 +/- 2.1 mm2 vs 10.4 +/- 1.8 mm2 at baseline, p < 0.05). After papaverine infusion, a trend toward a vasoconstricting effect was observed in response to increased flow in group 1 (10 +/- 1.3 mm2 vs 11.4 +/- 1.2 mm2 at baseline, p < 0.05). that was not observed in group 2 (9.4 +/- 2 mm2 vs 8.9 +/- 1.9 mm2, p = NS). Linsidomine infusion induced a significant vasodilating effect in both groups (p < 0.001). In conclusion, intravascular ultrasound may be considered a useful tool to assess endothelial function of large coronary arteries and to obtain the precise relationship between wall thickness and the vasomotor response.

Effects of endogenous atrial natriuretic peptide released by rapid atrial pacing in dogs

The relationships between the hemodynamic, renal, and endocrine changes induced by rapid atrial pacing were studied in seven chloralose-anesthetized greyhounds paced from the right atrial appendage for 60 min at 250 beats/min. Pacing increased mean pulmonary wedge pressure, decreased cardiac output, and decreased mean arterial pressure. Systemic vascular resistance did not change significantly. Coronary sinus atrial natriuretic peptide (ANP) concentrations rose maximally within 5 min of commencing pacing. The corresponding increase in arterial ANP concentrations during this time was only 44% of its maximum value after 30 min of pacing. Plasma concentrations of arginine vasopressin were unchanged. Plasma renin activity decreased during pacing and showed a marked rebound increase at 60 min postpacing. Plasma norepinephrine levels did not change significantly during pacing. Urine flow increased during the latter 30 min of pacing. There was no significant change in sodium clearance despite high sustained concentrations of ANP. The lack of significant natriuretic and systemic vasodilator effects in association with high arterial plasma concentrations of endogenous ANP, in the absence of antagonistic mechanisms, suggests that the natriuretic and vascular effects of ANP may not be its major physiological actions.

Vasoactive effects of eicosapentaenoic acid on isolated vascular smooth muscle.

Dietary intake of unsaturated fatty acid of eicosapentaenoic acid (EPA) is thought to reduce the size and incidence of myocardial infarction. These beneficial effects are postulated to be due to chronic antithrombotic properties of EPA itself. We studied the possible direct effects of EPA on vascular smooth muscle as well as the ability of EPA to modify the vasoactivity of constrictor mediators in rabbit and cat aortic rings and isolated cat coronary arteries. EPA concentration-dependently (30 to 300 microM) relaxed rabbit and cat aortic rings having an intact endothelium, while EPA did not show any significant vasodilator effects on rings without an endothelium. This EPA-induced vasorelaxation was not altered by the cyclooxygenase inhibitor ibuprofen, but was totally abolished by the guanylate cyclase inhibitor methylene blue, indicating an endothelium-dependent smooth muscle relaxation mechanism. In isolated perfused cat coronary arteries, EPA (3 to 300 microM) exerted a dilator effect which was endothelium-independent and not affected by ibuprofen. The response was attenuated by propyl gallate, a lipoxygenase inhibitor. EPA also inhibited leukotriene (LT) C4, (50 nM) and LTD4 (50 nM)-induced vasoconstriction of isolated cat coronary arteries ranging from a blockade of 10% to 15% (P less than 0.05) at 3 microM of EPA to a blockade of 89% to 93% (P less than 0.01) at 300 microM. In contrast, the thromboxane analog, CTA2, induced coronary constriction was not significantly altered by EPA. Thus, EPA produces endothelium-dependent relaxation in rabbit and cat aorta and endothelium-independent vasodilation in cat coronary arteries (i.e., intact vessels or helical strips). Moreover, EPA exerts acute anti-leukotriene actions in coronary arteries. In the case of long-term dietary intake of EPA, these actions may contribute to the protective action of EPA in myocardial ischemia.

Experimental study of the isolated canine kidney perfusion with special reference to effects of various vasodilator agents.

Perfusions of 34 isolated canine kidneys were performed at 38°C using heparinized diluted homologous blood, and the effects of vasodilators on renal circulation and urinary output were studied. Renal pressure, renal blood flow, renal vascular resistance, urine volume, glomerular filtration rate by creatinine clearance method, and intrarenal distribution of blood flow by 131I-tagged serum albumin method were measured before and after the administration of drugs, and the following results were obtained. Papaverine and mannitol were effective in improving the circulation through the isolated kidney when proper doses were given. ATP showed biphasic effects depending on its concentration. Phenoxybenzamine isoproterenol and bradykinin showed no significant vasodilating effect on the isolated kidney perfusion.

Intra-arterial Administration of Procaine Hydrochloride After Arteriography

In spite of earlier investigator's reports, detailed oscillometric evaluation of peripheral circulation has not produced proof of a significant vasodilating effect of procaine hydrochloride in a series of 55 patients. No blood pressure alteration or other adverse effects occurred. However, prior to the intra-arterial administration of procaine, clinically significant arteriospasm was observed in 38 of 885 arteriographic procedures. After the routine use of procaine, clinical arteriospasm was observed in only two of 1,197 arteriographic procedures, and no arterial or venous thromboses complicated arteriography.