Abstract-Recently a point mutation of guanine to thymine at nucleotide position 1917 in the endothelial nitric oxide synthase (eNOS) gene has been reported to be associated with coronary artery spasm. In addition, a significant association of the 4a/b polymorphism in intron 4 of the eNOS gene with coronary artery disease has been reported. However, the implications of these polymorphisms with respect to acute myocardial infarction (AMI) remain to be established. We conducted a case-control study of 226 patients with AMI and 357 healthy gender-and age-matched control subjects. In the former group, coronary angiograms were evaluated according to angiographic criteria based on the number of diseased vessels (Ն75%) and the number of stenotic lesions (Ն50%). Homozygosity for the Glu-Asp298 polymorphism existed in 5 of 226 patients with AMI (2.2%) but not in any of the 357 control subjects (Pϭ.0085). However, when we evaluated the coronary angiograms of 226 case patients, there was no difference in the number of diseased vessels or the number of stenotic lesions between the patients with this homozygote and those without it. By contrast, there was no evidence of a significant increase in the risk of AMI or the severity of coronary atherosclerosis among individuals with the a/a genotype of the eNOS4a/b polymorphism. Our results imply that patients who are homozygous for the Glu-Asp298 polymorphism may be genetically predisposed to AMI; however, this mutation apparently is not related to the severity of coronary atherosclerosis. Further studies are needed to confirm our results and characterize the molecular mechanisms by which eNOS is involved in susceptibility to AMI. (Hypertension. 1998;32:521-526.)Key Words: endothelium-derived relaxing factor Ⅲ genes Ⅲ myocardial infarction Ⅲ atherosclerosis Ⅲ angiography S ince the identification of nitric oxide (NO) as an important endothelium-derived relaxing factor, there has been an explosion of new information on the physiological and pathophysiological roles of NO. NO is synthesized from the amino acid L-arginine by a family of enzymes, referred to as NO synthase (NOS). Three distinct isoforms of NOS have been identified to date.1 The inducible NOS is expressed in vessel walls and macrophages by certain cytokines and endotoxin lipopolysaccharides in pathological conditions. 2The constitutive neuronal NOS is expressed in the central and peripheral nervous systems as well as in macula densa of kidney. It plays important roles in physiological 3 and pathophysiological 4 conditions. The constitutive endothelial NO synthase (eNOS) is expressed in the endothelium, where it produces NO from L-arginine. NO diffuses from the endothelium to the vascular smooth muscle cells, where it increases the concentration of cGMP by stimulating soluble guanylate cyclase, leading to vascular relaxation.

Muscle cells are frequently subjected to severe conditions caused by heat, oxidative, and mechanical stresses. The small heat shock proteins (sHSPs) such as αB-crystallin and HSP27, which are highly expressed in muscle cells, have been suggested to play roles in maintaining myofibrillar integrity against such stresses. Here, we identified a novel member of the sHSP family that associates specifically with myotonic dystrophy protein kinase (DMPK). This DMPK-binding protein, MKBP, shows a unique nature compared with other known sHSPs: (a) In muscle cytosol, MKBP exists as an oligomeric complex separate from the complex formed by αB-crystallin and HSP27. (b) The expression of MKBP is not induced by heat shock, although it shows the characteristic early response of redistribution to the insoluble fraction like other sHSPs. Immunohistochemical analysis of skeletal muscle cells shows that MKBP localizes to the cross sections of individual myofibrils at the Z-membrane as well as the neuromuscular junction, where DMPK has been suggested to be concentrated. In vitro, MKBP enhances the kinase activity of DMPK and protects it from heat-induced inactivation. These results suggest that MKBP constitutes a novel stress-responsive system independent of other known sHSPs in muscle cells and that DMPK may be involved in this system by being activated by MKBP. Importantly, since the amount of MKBP protein, but not that of other sHSP family member proteins, is selectively upregulated in skeletal muscle from DM patients, an interaction between DMPK and MKBP may be involved in the pathogenesis of DM.

A close relationship between obesity and hypertension has been recognized, and plasma angiotensinogen concentrations (p-AGT) have been reported to correlate with blood pressure (BP). However, little is known about AGT in obese patients with hypertension. To define the role of AGT in obese hypertension, we measured p-AGT in obese patients. The subjects were 42 obese patients diagnosed on the basis of a body mass index (BMI) of more than 25 kg/m2, and 21 sex- and age-matched nonobese patients, whose BMI was less than 25 kg/m2. The hypertensive patients had not previously received antihypertensive drugs. P-AGT (P < .05) and mean BP (P < .0001) was increased in the obese patients as compared with the nonobese patients. Positive correlations were observed between BMI and p-AGT, mean BP and p-AGT, and BMI and mean BP (all P < .05). However, after adjustment for blood pressure, p-AGT was not different between groups, and after adjustment a positive correlation remained only between BMI and mean BP. These results suggested the possible involvement of increased p-AGT in hypertension in obese patients, although this may be a secondary change to hypertension or obesity.

The angiotensinogen (AGT) gene M235T variant is associated with essential hypertension and elevated plasma AGT concentrations, although the underlying mechanisms are unknown. Recent studies have suggested that AGCE 1 (human AGT gene core promoter element 1) located in the 5' upstream core promoter region (position -25 to -1) of the human AGT gene has an important part in the expression of AGT mRNA by binding with transcription factor AGCF 1 (human AGT gene core promoter element binding factor 1), and a mutation at -20 from adenine to cytosine (A-20C) increases the level of expression of this transcript. We therefore examined subjects with this mutation to study the association with increased plasma AGT concentrations and with essential hypertension. One hundred eighty-eight subjects receiving no antihypertensive medication were examined with regard to the correlation between A-20C and plasma AGT concentrations, and 234 subjects were studied with respect to the association between A-20C and essential hypertension. A-20C was determined by polymerase chain reaction-restriction fragment length polymorphism analysis with EcoOR 109I. Multiple regression analysis showed a weak but significant correlation between A-20C and plasma AGT concentrations (P=.047) and essential hypertension (P=.049). The results suggest that A-20C may underlie the increase in plasma AGT concentrations and be involved in the development of essential hypertension.

Angiotensinogen gene-knockout (Atg-/-) mice lacking angiotensin II exhibit chronic hypotension. The present study was designed to investigate pathophysiology of Atg-/- mice from the renal functional view. Wild-type (Atg+/+) and Atg-/- mice at 10 weeks of age were housed in metabolic cages for 24-hour urine collection. When provided free access to water, Atg-/- mice showed an increased urine output and a decreased urine osmolality compared with Atg+/+ mice. Urinary excretion and plasma levels of vasopressin were significantly higher in mutant mice than in wild-type mice. On the other hand, urinary excretion of aldosterone in mutant mice was suppressed to the levels under the detection limit of the assay system. The mean plasma aldosterone level of Atg-/- mice was suppressed to 30% of that of Atg+/+ mice. Plasma levels of creatinine, endogenous creatinine clearance, and urinary electrolyte excretion were not different between these mice. In Atg+/+ mice, urine osmolality was markedly increased from 1929 +/- 21 to 3314 +/- 402 mOsm/kg during water deprivation, whereas this parameter in Atg-/- mice did not change significantly (from 1413 +/- 121 to 1590 +/- 92 mOsm/kg). Urinary vasopressin excretion increased during water deprivation from 0.24 +/- 0.04 and 0.70 +/- 0.08 to 0.42 +/- 0.06 and 2.31 +/- 0.35 ng/mg creatinine in wild-type and mutant mice, respectively. Histologic study revealed interstitial inflammation, and atrophic changes in the tubules and papilla in Atg-/- mice. In conclusion, a genetic deficiency of angiotensinogen produced an impaired urine concentrating ability and tubulointerstitial lesions, indicating the critical role of angiotensinogen in developing normal tubular function and construction.

During admission for investigation of dysphagia, an 82-year-old woman suddenly complained of dyspnea, which was followed by cardiogenic shock. Her symptoms, electrocardiogram, echocardiogram and laboratory data were compatible with an extensive acute anterior myocardial infarction. Emergency cardiac catheterization showed no atheromatous narrowing in any coronary artery. However, the contractions of the left and right ventricles were diffusely and severely impaired, except for some hyperkinesis of the basal area. The asynergy, as well as the abnormalities on the ECG, improved almost to normal by the 35th hospital day. An endomyocardial biopsy from the right ventricle during the acute phase showed atypical myocardial damage with proliferation of fine collagen fibers and small round-cell infiltration including polymorphologic leukocytes. This type of transient cardiac disorder has recently been described in Japan, and is called 'Tako-tsubo cardiomyopathy' because of the characteristic appearance of the left ventricular asynergy. In the present case, ventricular asynergy was not limited to the left ventricle, but was also present in the right ventricle.

Hemodynamic and endocrine factors are among the most important factors implicated in the physiology and pathophysiology of the vascular wall. Arterial hypertension evokes structural and functional changes of the vascular wall (1, 2). Modifications of the extracellular matrix, including fibronectin (FN) 1 and collagen, have been previously reported in vessel walls of hypertensive animals (3-5). Activation and qualitative changes in the extracellular matrix participate in vascular wall remodeling and in the pathogenesis of atherosclerosis. Vascular remodeling in hypertension may be an adaptive response to increased transmural pressure (6 -9). Mechanical stress seems to play a direct role in vascular remodeling, since mechanical stretch is able to increase protein synthesis by vascular smooth muscle cells (VSMCs) (10). However, neuronal and humoral factors may be critical in hypertension-induced remodeling of vascular wall. Especially, several in vivo studies have reported that hypertension activates the vascular renin-angiotensin system (RAS) including angiotensin-converting enzyme (ACE) (11), and infusion of pressor and subpressor doses of angiotensin II (Ang II) increases aortic FN mRNA in both hypertensive and normotensive animals (12, 13). Ang II evokes diverse physiological response including arterial vasoconstriction to elevate blood pressure in vivo (14) and increases production of collagen with a growth-promoting effect on VSMCs in vitro (15). Pharmacological evidence has defined at least two subtypes of Ang II receptors, Ang II type 1 (AT1) receptor and Ang II type 2 (AT2) receptor. Previous results of molecular cloning have revealed that both receptor subtypes belong to the superfamily of G protein-coupled receptors with seven transmembrane helices (16 -19). According to the recent results of in vitro studies, Ang II initially activates a phosphatidylinositol-specific phospholipase C (PI-PLC) via its binding to AT1 receptor on the surface of VSMCs, leading to the generation of inositol triphosphate and diacylglycerol (20), which are involved in intracellular Ca 2ϩ mobilization (21) and protein kinase C (PKC) activation (22), respectively. In VSMCs, Ang II also induces a rapid increase in expression of the growth-associated nuclear protooncogenes and stimulates tyrosine phosphorylation of multiple substrates (23, 24). These findings, taken together with relatively abundant expression of AT1 receptor in vascular wall and VSMCs, indicate that Ang II plays an important role in vascular remodeling via an AT1 receptor pathway. Thus, investigation of the mechanism of Ang II-induced regulation of extracellular matrix and tissue RAS in VSMCs is essential in elucidating the mechanism of vascular remodeling and the pathogenesis of atherosclerosis.In the present study, we examined the effects of Ang II on gene expression of extracellular matrix components (FN and

Angiotensinogen is expressed in many tissues besides the liver. Recent studies have suggested that abnormalities in the regulation of angiotensinogen gene expression may be involved in the development of hypertension. However, little information is available concerning the functional significance of tissue angiotensinogen. In this study, we measured plasma angiotensinogen concentration by radioimmunoassay and examined the expression of tissue angiotensinogen by Northern blot analysis in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Although plasma angiotensinogen concentration in SHR was comparable to that in WKY at 6 weeks of age, it was increased significantly at 14 weeks of age in SHR and became higher than that in WKY. The levels of hepatic angiotensinogen mRNA were similar in SHR and WKY, and the levels of aortic, adrenal, and renal angiotensinogen mRNAs were lower in SHR than in WKY at both 6 and 14 weeks of age. Brain angiotensinogen expression in SHR was higher than in WKY at 6 weeks of age and was comparable to that in WKY at 14 weeks of age. On the other hand, cardiac and fat angiotensinogen mRNA levels were significantly increased at 14 weeks of age in SHR. These results demonstrate that the expression of tissue angiotensinogen is regulated differently in SHR and WKY and indicate that the development of hypertension is accompanied at least temporally with increases in plasma angiotensinogen concentration as well as cardiac and adipogenic angiotensinogen mRNA in SHR.