永井 良三

We studied the role of nitric oxide (NO) synthesis in amelioration of blood pressure elevation during dietary salt loading in transgenic mice overexpressing sodium proton exchanger. Systolic blood pressure rose after starting salt loading only in the high-salt group of transgenic mice. However, this elevation of blood pressure was not continued. Urinary excretion of inorganic nitrite and nitrate in the high-salt group of transgenic mice was significantly higher than in the high-salt group of control mice. These results suggest that increased NO synthesis in response to salt loading is one of the anti-hypertensive mechanisms in transgenic mice overexpressing sodium proton exchanger.

To determine whether ANG II as well as mechanical stress affect the production of tumor necrosis factor (TNF) in the heart, neonatal rat cardiac myocytes and fibroblasts were cultured separately and treated for 6 h with ANG II, lipopolysaccharide (LPS), or cyclic mechanical stretch. LPS induced the production of TNF in cardiac myocytes and fibroblasts. However, TNF synthesis in fibroblasts was 20- to 40-fold higher than in myocytes. ANG II (>/=10(-8) M) and mechanical stretch stimulated the production of TNF in cardiac fibroblasts but not in myocytes. Furthermore, both ANG II and LPS increased the expression of TNF-alpha mRNA in cardiac fibroblasts. Isoproterenol inhibited both LPS- and ANG II-induced production of TNF in cardiac fibroblasts with increasing intracellular cAMP level. Moreover, both isoproterenol and dibutyryl cAMP inhibited LPS-induced TNF-alpha mRNA expression. Thus activation of the renin-angiotensin system, as well as mechanical stress, can stimulate production of TNF in cardiac fibroblasts. Furthermore, beta-adrenergic receptors may be responsible for the regulation of TNF synthesis at the transcriptional level by elevating intracellular cAMP.

Na+-H+ exchange inhibitors may reduce myocardial damage after reperfusion. However, their effects on microvascular deterioration are not known. We examined the potency of a novel Na+-H+ exchange inhibitor, SM-30550 [ N-(Aminoiminomethyl)-1,4-dimethyl-1H-indole-2-carboxamide methanesulfonate], and its effects on microvascular damage after reperfusion. In an in vitro study. the Na+-H+ exchange inhibiting activity of SM-20550 was about 10 times greater than that of ethylisopropyl amiloride. In in vivo experiments, we occluded the left circumflex coronary artery in 29 dogs for 2 h and then reperfused for 5 h. SM-20550 was administered either before ischemia (n = 11) or before reperfusion (n = 7). Another 11 dogs served as controls. We found that SM-20550 not only improved coronary vasodilator responses to acetylcholine and adenosine after reperfusion, but also reduced infarct size (P < 0.01). Intramyocardial bleeding, which should reflect microvascular damage, was not found in dogs with SM-20550 treatment. Infarct size was correlated inversely with collateral blood flow in control (both, P < 0.01) but not in SM-20550-treated animals. Furthermore, SM-20550 significantly suppressed ventricular fibrillation during both ischemia and reperfusion. These results suggest that protective effects of Na+-H+ exchange inhibitors on reperfused myocardium are due at least in part to microvascular protection. (C) 1999 Elsevier Science B.V. All rights reserved.

We examined the expression of smooth muscle cytoskeleton in spindle-shaped cells in the capsule of hepatocellular carcinoma (HCC) and the septa of liver cirrhosis (LC). Serial sections of livers resected from 11 patients were stained with monoclonal antibodies against vimentin, desmin, smooth muscle actin (1A4, HHF35, CGA7) and smooth muscle myosin heavy chain isoforms (SM1, SM2). Capsular spindle-shaped cells exhibited a cytoskeletal feature indicative of intermediately differentiated smooth muscle cells. Computer-assisted morphometry revealed that the proportions of 1A4-, HHF35-, CGA7- and SM1- positive areas to vimentin-positive area were 88.0+/-11.0%, 50.8+/-17.4%, 25.3+/-16.4% and 19.4+/-12.4% (n=11) in main rumours and 86.6+/-9.4%, 50.9+/-18.7%, 21.1+/-12.3% and 17.6+/-9.7% (n=12) in daughter rumours, indicating that spindle-shaped cells are heterogeneous in cytoskeletal expression. Septal spindle-shaped cells in LC lacked the cytoskeletal proteins specific to differentiated smooth muscle cells (CGA7, SM1, SM2 and desmin). Electron microscopically, capsular spindle-shaped cells contained more microfilaments and less rough endoplasmic reticulum than do septal cells. Intermediately differentiated smooth muscle cells are induced in the capsule of HCC but not in the septa of LC, suggesting a role for stromal interaction by tumour cells in the induction of smooth muscle cells.

It has been well recognized that patients with major coronary risk factors develop atherosclerosis in a higher frequency, but there are many atherosclerotic patients without these risk factors, suggesting the presence of other unknown risk factors regulating development of atherosclerosis. It has been known that the most important risk factor for atherosclerosis is "aging" to whatever extent the major risk factors are involved in atherogenesis. We recently identified the klotho gene as a possible regulator of human aging process. Because endothelial function is impaired in aged subjects, it is plausible to hypothesize that klotho may protect against endothelial dysfunction. Therefore, we decided to examine whether the klotho-deficient mice have endothelial dysfunction. We first found that the klotho gene product itself or its metabolites protect against endothelial dysfunction as a humoral factor because endothelium-dependent arterial dilatation was impaired in the klotho-deficient heterozygous mouse, which was improved by establishing parabiosis with a wildtype mouse but not with a heterozygous mouse. Reduced expression of the klotho gene seems to be a risk factor of arterial diseases because heterozygous mouse with apparently normal histology of the arterial wall developed hypertension with high-salt drinking water and atherosclerosis with high cholesterol diet. We also have shown that in animal models of hypertension, kidney diseases, hyperlipidemia and diabetes, all of which are known as an important risk factor for atherosclerosis, klotho gene expression was reduced in kidney. It is noteworthy that endothelial dysfunction observed in a rat model of hyperlipidemia and hyperglycemia (OLETF rat) could be improved by angiotensin converting enzyme inhibitor, which is accompanied by increased klotho gene expression in kidney. Our results suggest that klotho gene expression is regulated by local or systemic stress against kidney or the vascular wall.

The significance of the time from anaerobic threshold to respiratory compensation point (RCP-AT time) in patients with chronic heart failure was investigated. Thirty-seven patients with chronic heart failure (New York Heart Association class II or III) were enroled into the study. Cardiopulmonary exercise testing was performed using breath-by-breath gas sampling. A bicycle ergometer was used, and incremental exercise testing was carried out. Anaerobic threshold, respiratory compensation point (RCP), and the slope of oxygen uptake ((V) over dot O-2) as a function of work rate (Delta(V) over dot O2/Delta WR) were measured. A positive correlation (r=0.53) between RCP-AT time and Delta(V) over dot O2/Delta WR was found. RCP-AT time was corrected for the whole exercise period (ramp exercise-RCP point), and the correlation between corrected RCP-AT time and Delta(V) over dot O2/Delta WR was still present (r=0.46). There was no correlation between RCP-AT time and anaerobic threshold. These findings suggest that RCP-AT time is a new parameter that reflects the rate of the aerobic and anaerobic metabolism after AT.

The excessive pressor response triggered in patients by an alerting reaction to a doctor's presence has been termed the "white coat effect." A 68-year-old man with verbal apraxia after multiple lacunar infarctions was referred to the hospital for speech rehabilitation. He experienced difficulty in talking with the speech therapist during therapy sessions but not when talking with his friends or family. Because the therapist's presence was stressful to the patient, it was considered that his anxiety might produce an excessive increase in blood pressure. Blood pressure monitoring was performed during 2 separate days of speech therapies consisting of two sessions each. In one session, therapy was directed by the therapist; in the other, therapy was self-directed. The therapist-directed approach substantially increased both systolic and diastolic blood pressures, whereas the self-directed therapy slightly increased only systolic pressure. It was concluded that the excessive pressor response seen in this patient during therapist-directed speech therapy resulted from the white coat effect induced by the therapist's presence.