Nitric oxide synthase genes: candidate genes among many others

Inhibition of nitric oxide synthesis for four days induces vascular abnormalities and myocardial infarct areas but not significant arterial hypertension

BACKGROUND: Nitric oxide is an endothelium vasorelaxing factor and at least in some cases is the main cause of arterial hypertension, which is one of the most important risk factors of cardiovascular diseases. In Brazil, cardiovascular diseases are the first cause of mortality, representing about 30% of the total deaths. The L-NAME (Nω-nitro-arginine-methyl-ester) blocks the nitric oxide synthesis necessary to maintain the normal arterial pressure. OBJECTIVE: To study lesions in myocardium due to the inhibition of nitric oxide synthesis during four days (via L-NAME oral administration, concentration: 75 mgs versus 100 mL-1). METHODS: Fourteen normotensive young adults Wistar rats were submitted, during four days, to L-NAME. Six rats were utilized as the Control Group. At day 4 of the experiment, the animals were anesthetized, weighed, and their thoraxes were opened, and the cardiotomy was performed. The hearts were weighed, fixed, and processed using routine methods, and they were sectioned in 3 µm and stained. RESULTS: Abnormalities were observed in the wall of arterial vessels of any dimension, as vascular damage with increasing wall thickness related mainly to proliferation of arterial smooth muscle cell in submitted animals. Proliferation of cells in the intimal layer and its thickening were also observed in small arterial vessels (arteriole). Infarct areas were present. CONCLUSIONS: The present data suggested that inhibition of nitric oxide synthesis for four days induces vascular abnormalities and myocardial infarct areas, but not arterial hypertension.

Ambulatory blood pressure, left ventricular mass and vascular phenotypes in relation to the endothelial nitric oxide synthase gene Glu298Asp and intron 4 polymorphisms in a population-based family study

Reduced nitric oxide production is associated with pathological changes in the cardiovascular system. In a study of randomly chosen families, we analysed the relationship between two polymorphisms (Glu298Asp and intron 4) of the endothelial nitric oxide synthase (eNOS) and ambulatory blood pressure (ABP), left ventricular mass index (LVMI) and vascular phenotypes. The study population consisted of 127 parents and 167 offspring. All subjects underwent 24 h ABP monitoring using a SpaceLabs 90207 device. 2D and M-mode echocardiograms were obtained. Pulse wave velocity between the common carotid and femoral artery was measured with the Complior device, and the carotid intima-media thickness (IMT) was assessed by ultrasound. For statistical analysis, covariables and correlations between relatives were taken into account. The frequency of genotypes was as follows: for Glu298Asp: 55.1%-Glu/Glu, 40.1%-Glu/Asp and 4.8%-Asp/Asp; for intron 4: 65.0%-4 b/b, 33.3%-4 b/a and 1.7%-4 a/a, being in Hardy-Weinberg equilibrium (P > or = 0.29). There was no relationship between the eNOS gene polymorphisms and ABP or LVMI either in parents or their offspring. Among parents, carriers of the 298Asp allele had higher IMT values as compared with Glu/Glu homozygotes (0.94 vs 0.70 mm; P = 0.007). Among offspring, there was a similar tendency (0.60 vs 0.53 mm; P = 0.10), which was confirmed by transmission disequilibrium tests for quantitative variables (P > or = 0.07). Our findings indicate that the Glu298Asp polymorphism of eNOS identifies patients with larger carotid IMT, also in younger subjects.