Although blunted cardiac response to sympathetic stimulation in patients with heart failure is usually attributed to myocardial beta₁-adrenoceptor downregulation secondary to elevated circulating catecholamines, cardiomegaly per se may also play a role through presynaptic mechanisms such as reduction in cardiac norepinephrine (NE) concentration. To evaluate effects of cardiac dilatation on cardiac response to sympathetic stimulation, we studied left ventricular contractile and heart rate responses to plasma NE levels increased by exercise in 10 asymptomatic patients with a dilated left ventricle due to aotric regurgitation (AR), but with normal resting plasma NE levels, using 10 normal subjects and 10 patients with heart failure due to dilated cardiomyopathy (DCM) as controls. Plasma NE levels, systemic blood pressure, echocardiograph left ventricular dimensions, and heart rate were measured at rest, and at 3 submaximal levels of supine bicycle exercise. The ratio of peak systolic blood pressure to end-systolic dimension (P/D ratio), heart rate, and plasma NE increased with the intensity of exercise. In each subject, both P/D ratio and heart rate increased in a logarithmic manner against plasma NE levels. The solpe of the regression line for log (plasma NE)-P/D ratio relation, and that for log (plasma NE)-heart rate relation, were significantly less in patients with AR than in normal subjects (p<0.001 and p<0.05, respectively), and were less in patients with DCM than in patients with AR (p<0.005 and p=0.051, respectively). Thus, the left ventricular contractile and heart rate responses to sympathetic stimulation are blunted in patients with dilated hearts due to AR, even in the absence of overt heart failure and elevated plasma NE levels. These responses were further de-creased in patients with heart failure due to DCM. Cardiac responses to sym-

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A 64-year-old man with total occlusion of the left main coronary artery associated with acute anterior infarction was treated successfully with combined emergency intracoronary thrombolysis and coronary bypass surgery. Postoperative angiography demonstrated patent bypass grafts with good preservation of left ventricular function.

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Changes in cytosolic calcium concentration ([Ca²+]i) have been implicated in the regulation of intracellular pH (pHi) in several cell types. In the present study we investigated the regulatory mechanism of Na⁺/H⁺ exchange induced by angiotensin II (AII) in cultured rat vascular smooth muscle cells (VSMCs). Serially passaged VSMCS from Sprague-Dawley rat thoracic aorta were grown on coverslips and loaded with the pH-sensitive fluorescent indicator 2', 7'-bis (carboxyethyl)-5, 6-carboxyfluorescein (BCECF). In HCO₃-free Ringer solution, pH 7.40, the resting pHi was 7.21±0.01 (n=21). A biphasic response was seen after exposure of these cells to AII: an initial transient a acidification, followed by sustained alkalization. The magnitude of alkalization was dose-dependent. AII-mediated acidification was completely inhibited by [Sar¹-Iie⁵-Gly⁸]AII, but amiloride had no effect. In contrast, the alkalization induced by AII was abolished by both amiloride and Na⁺-free medium. In Ca²⁺-free medium, the AII-induced alkalization was partially blocked and verapamil also caused partial inhibition. Since AII activates phospholipase C in VSMCs, we examined whether AII would increase Na⁺/H⁺ exchange by activation of protein kinase C. An inhibitor of protein kinase C, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7), partially inhibited the alkalization induced by AII. These results indicate that AII stimulates cytoplasmic alkalization via an amiloride-sensitive Na⁺/H⁺ exchange system in cultured rat VSMCs, and that this AII-stimulated Na⁺/H⁺ exchange is mediated by Ca²⁺-dependent and protein kinase C-dependent mechanisms.

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The accumulation of both Inositol-(1, 4, 5)-trisphosphate (IP₃) and Inositol-(1, 3, 4, 5)-tetrakisphosphate (IP₄) after hormonal stimulation has a physiological role, possibly in altering Ca²⁺ levels in cardiac tissue. However, the accumulation of inositol polyphosphate under pathophysiological conditions has not been studied. In our experiments the metabolism of phatidylinositol and IP₃ m cardiac myocytes as investigated. It was shown that basal levels of cytosolic phosphatidylinositol specific phospholipase C (PI-PLC), phosphatidylinositol-(4, 5)-bisphosphate specific phospholipase C (PIP₂-PLC) activities markedly increased in stroke-prone spontaneously hypertensive rats (SHRSP) with age compared with age matched Wistar Kyoto rats (WKY). IP₃ kinase and IP₃ phosphatase activities also increased in SHRSP hearts with age. Their activities increased in WKY, but to a lesser antent than in SHRSPs. These data suggest that a PI turnover pathway such as the phosphatidylinositol 4, 5-bisphosphate-IP₃-Ca²⁺ pathway or the diacylglyceride-protein kinase C pathway may have an important role in the development of hypertrophy in SHRSP heart.

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On the basis of the detection of the enteroviral RNA in the hearts of patients with healed myocarditis and dilated cardiomyopathy, we investigated cardiac viral persistence in experimental myocarditis. Weanling C3H/He mice were given myocarditis by inoculation with coxsackievirus B3 (Nancy strain), and their hearts were examined by genomic studies and viral isolation up to the 180th day after inoculation. The virus was isolated from the heart until the 9th day. By slot-blot hybridization, viral RNA was also only detected until the 9th day in the heart. Specific DNA amplification using the polymerase chain reaction (PCR) was performed after a reverse transcriptase reaction, then followed by Southern blot hybridization with a ^<32&ct;P-labelled oligomer probe. This technique achieved the type-specific detection of coxsackievirus B3 even at a level of less than one of the 50% tissue culture infective dose (TCID₅₀). With this technic, viral RNA was detected up to the 28th day after inoculation. Thus, the viral RNA persisted in the hearts of these mice even when infectious virus could no longer be detected.

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In vascular tissues, many types of stimulants which release endothelium-derived relaxing factor (EDRF) hyperpolarized the smooth muscle membrane in an endothelium-dependent manner. The hyperpolarizations were resistant to inhibitors of the actions of EDRF, thereby suggesting that they were elicited by an unidentified substance called endothelium-derived hyperpolarizing factor (EDHF). The EDHF induced hyperpolarization was produced by an increase in K⁺-permeability of the membrane, and was one of the factors to induce endothelium-dependent vasodilations. Release of EDHF required an increase in endothelial Ca<2+>, due eithr to release of Ca<2+> from intracellular storage or to its influx from the external media.

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We have found that vascular injuries are induced by intravascular aggregation of platelets activated by arachidonic acid (AA) or ADP. The characteristic findings are the appearance of vacuoles in endothelial cells and eventual deendothelialization. In deendothelialized regions, formation of platelet thrombi was observed. The platelets in the thrombi were stained with 2T60, a monoclonal antibody that recognizes activated platelets. The change was more remarkable in the AA-injected animals because AA has a stronger platelet activating effect and a detergent effect on the endothelium. The ADP-injection experiments clarified the role of platelets in vascular injury. These findings suggest that activated platelets play a role in the genesis of vascular injuries, and that their role is related to thrombus formation.

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Thrombomodulin is an endothelium-associated glycoprotein that coverts thrombin from a procoagulant protease to an anticoagulant. Thrombin, a key enzyme in thrombus formation, binds to thrombomodulin on the endothelium. However after thrombin binds to thrombomodulin, it fails to act on the coagulation factors and platelets, and its ability to activate protein C is enhanced more than 1, 000-fold. This article reviews the recent progress in the study of thrombomodulin.

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The localization of tissue factor (TF) in atherosclerotic plaques of human aortas was immunohistochemically examined using rabbit anti-IgG against recombinant TF, which was expressed in E. coli. TF, the initiator of the extrinsic coagulation pathway, was ubiquitously present in atherosclerotic intima, and was expressed mainly by macrophages, but not by endothelial cells. It has been suggested that some macrophages in atherosclerotic intima co-express both molecules of TF and platelet-derived growth factor-B chain. We have developed a morphometrically quantitative in vitro assay for angiogenesis, using endothelial cultures on collagen gel incorporating plasminogen. With this method, we have obtained findings suggesting that plasminogen and plasminogen activators (PAs), especially urokinase-type PA (uPA) derived from endothelial cells, enhance angiogenic activity, probably by increasing endothelial migration. uPA was immunohistochemically observed to be primarily cell-associated on the focal contract areas, probably via its receptors on endothelial cells. These findings may support the hypothesis that the activation and regulation of the pericellular fibrinolysis system is closely related to angiogenesis.

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