[Multiple cavities in myocardium of left ventricle after irradiation therapy for breast cancer: a case report].

A 68-year-old woman was admitted to our hospital with congestive heart failure. She had been diagnosed with hypertrophic cardiomyopathy 12 years ago in another hospital. She had received irradiation therapy for left breast cancer 33 years ago after resection of her left breast. Echocardiography revealed left ventricular hypertrophy and wall motion hypokinesis, and multiple cavities in the myocardium of the left ventricle, interventricular septum, and anterior wall. Some cavities were observed to connect to the left ventricular cavity and Doppler echocardiography showed slow velocity flows in them different from that of the coronary artery. The pathologic diagnosis was severe sclerosis of the left coronary artery, especially the left descending artery and its branch, which was the area with irradiation. Histopathology revealed sclerotic changes of the coronary artery causing acute and chronic myocardial infarction, and incomplete regeneration and hypertrophy of cardiac cells. There was no sign of hypertrophic cardiomyopathy. Myocardial degeneration and deciduation were present next to the cavities connected to left ventricle-like fistulas.

Lysophosphatidylcholine inhibits endothelium-dependent hyperpolarization and N omega-nitro-L-arginine/indomethacin-resistant endothelium-dependent relaxation in the porcine coronary artery.

BACKGROUND: Oxidized LDL and lysophosphatidylcholine (LPC) have been reported to inhibit the endothelium-dependent relaxation (EDR) mediated by nitric oxide. Recently, a new vasorelaxing factor, endothelium-derived hyperpolarizing factor (EDHF), which hyperpolarizes and relaxes the porcine coronary artery in the presence of N omega-nitro-L-arginine (NNA) and indomethacin (IM), has been reported. We examined whether LPC also inhibits both the EDHF-mediated relaxation and membrane hyperpolarization of the porcine coronary artery. METHODS AND RESULTS: EDHF was evaluated as the bradykinin- or A23187-induced relaxation of the porcine coronary artery contracted by prostaglandin F2 alpha in the presence of NNA and IM. We also directly measured the membrane potential of the porcine coronary artery. The effects of LPC on both relaxation and membrane hyperpolarization were investigated. At concentrations of 0 to 20 mumol/L, LPC dose-dependently inhibited the NNA/IM-resistant EDR induced by bradykinin and A23187, and the relaxation was reversible after the absorption of LPC with albumin. LPC also inhibited the bradykinin- and A23187-induced hyperpolarization of the porcine coronary artery. CONCLUSIONS: In the present study, LPC was found to inhibit not only nitric oxide-mediated but also EDHF-mediated relaxation of the porcine coronary artery. Our findings suggest a new regulatory mechanism in the atherosclerotic coronary artery.

Long-term prognosis after thrombolytic therapy for acute myocardial infarction.

In order to clarify the relationship between the patency of the infarcted arteries and subsequent long-term prognosis after thrombolytic therapy, we evaluated 116 patients with acute myocardial infarction treated with intracoronary (112 patients) or intravenous (four patients) urokinase. Patients treated with angioplasty after thrombolysis were excluded. The infarcted vessel was recanalized in 52 patients (patent group) and was not in the remaining 64 patients (occluded group). Five-year and 8-year follow up was conducted in 91% and 81% of the patients, respectively. The 1-, 5- and 8-year survival rate for the patent and occluded group was 91.8 and 80.9%, 80.8 and 79.2%, and 75.9 and 75.6%, respectively. The survival rate in the patent group tended to be higher than that in the occluded group up to 4 years. However, after 5 years, both groups showed similar survival rates. Therefore, reopening of the infarcted arteries with thrombolysis was not an independent predictor for late cardiac death (Cox regression analysis).

Structure and function of nitric oxide synthases.

Nitric oxide (NO), which accounts for the biological activity of endothelium-derived relaxing factor, is now thought to play a variety of roles in the nervous system and in immunologic reactions. NO is synthesized from L-arginine by nitric oxide synthase (NOS). There are three isoforms of NOS; type I (neuronal), type II (inducible), and type III (endothelial). The fundamental structure of the three isoforms, which contain calmodulin-, FMN-, FAD-, and NADPH-binding domains, is the same. Calmodulin is already bound to inducible NOS without requiring Ca2+, while the others are Ca2+/calmodulin-dependent. Endothelial NOS is bound to membranes by N-myristoylation, while the other isoforms are soluble. The human endothelial NOS gene has been cloned. It has several highly repetitive regions which could provide potential sites for DNA polymorphism. It might be of interest to examine the relationship between such polymorphism and cardiovascular disorders.

Preferential inhibition of inducible nitric oxide synthase by ebselen.

Ebselen, 2-phenyl-1,2-benzisoselenazole-3(2H)-one can preferentially inhibit the activity of inducible nitric oxide (NO) synthase with little inhibition of endothelial constitutive NO synthase within a certain concentration range. This suggests that ebselen deserves further in vivo studies to examine its possible application to the therapy of septic shock where inducible NO synthase is responsible for vasodilation.

Stabilization of inducible nitric oxide synthase by monoclonal antibodies.

We have produced 14 monoclonal antibodies to inducible nitric oxide synthase purified from rat peritoneal cytotoxic activated macrophages. None of the antibodies showed neutralizing activity, but some of them enhanced the enzyme activity through stabilization of the enzyme.

Purification of nitric oxide synthase from rat macrophages.

Nitric oxide (NO) synthase (EC 1.14.23) has been purified to apparent homogeneity from rat macrophages. The purification procedure involves affinity chromatography with adenosine 2',5'-diphosphate-agarose and gel filtration chromatography on a Superose 12 HR 10/30 column. The apparent molecular weight is 300,000 by gel filtration. On polyacrylamide gel electrophoresis in sodium dodecyl sulfate, the enzyme migrates as a single protein band with Mr = 150,000. The purified enzyme is colorless, and an absorption maximum is observed at 280 nm. The half-life of the enzyme activity is 6 h at pH 7.4 and 4 degrees C. The enzyme activity required the presence of NADPH, (6R)-5,6,7,8-tetrahydro-L-biopterin, and dithiothreitol. Although the cerebellar and endothelial enzyme require Ca2+ and calmodulin, these are not required by the macrophage enzyme. The macrophage nitric oxide synthase (an inducible enzyme) seems to be different from the cerebellar and endothelial enzyme (a constitutive enzyme).

Cytosolic and membrane-bound nitric oxide synthase.

Cytotoxic activated macrophages were sonicated and centrifuged. The activity of nitric oxide (NO) synthase was present in the supernatant and independent of Ca2+. The pellets were washed three times and treated with buffer containing 0.1% Triton X-100 or buffer alone, followed by centrifugation. The supernatant containing Triton X-100 showed NO synthase activity that was dependent on Ca2+, whereas the supernatant without the detergent had little activity. These data suggest that there are two forms of NO synthase: cytosolic and membrane-bound enzymes.

Calmodulin-independent nitric oxide synthase from rat polymorphonuclear neutrophils.

Recently, the purification of nitric oxide synthase (EC 1.14.23) from rat cerebellum has been reported, and the enzyme is a calmodulin-requiring enzyme (Bredt, D. S., and Snyder, S. H. (1990) Proc. Natl. Acad. Sci. U. S. A. 87, 682-685). In this paper, nitric oxide synthase has been purified to near homogeneity from the cytosol fraction of rat polymorphonuclear neutrophils. The purification procedure involves affinity chromatography with adenosine 2',5'-diphosphate-agarose and an anion exchange column, DEAE-Bio-Gel A. On polyacrylamide gel electrophoresis in sodium dodecyl sulfate, the enzyme migrated as a single protein band with Mr = 150,000. The molecular weight was estimated to be 150,000 by gel filtration on a Superose 12 HR 10/30. The purified enzyme was unstable with a half-life of 3 h at pH 7.4 and 4 degrees C. The enzyme activity required the presence of Ca2+, NADPH, FAD, and (6R)-5,6,7,8-tetrahydro-L-biopterin. Calmodulin antagonists (W5, W7, W13, and trifluoperazine dihydrochloride) did not inhibit the enzyme activity, and the addition of calmodulin was also ineffective for the increase in the enzyme activity. The neutrophil enzyme appears to be a calmodulin-independent type of nitric oxide synthase.

Stabilizing factor(s) of nitric oxide (NO) synthetase.

We found that the cytosol of rat peritoneal polymorphonuclear neutrophils contains factor(s) that can stabilize an unstable enzyme, nitric oxide synthetase, in the cytosol. This enzyme has been purified to a single protein from the cytosol. Its half-life was 3 hours at 4 degrees C and was prolonged to greater than 24 hours by the stabilizing factor in the cytosol. The molecular weight of the stabilizing factor was greater than 100,000. Its activity was lost by the treatment with heating or alkali for 1 min or with acid for 5 min. It did not adhere to the carboxymethyl or diethylaminoethyl column at neutral pH. This stabilizing factor(s) may play a role in the regulation of the nitric oxide synthetase.