| Research Abstract |
To clear the mechanisms of the diseases of the cardiac conduction system, it is necessary to biochemically investigate the internal changes by aging of cardiac conduction system. However, there is no hypersensitive assay to assess the intracellular functions of cardiac conduction cells. The aims of this study are to develop the hypersensitive assay of substances concerning with the intracellular nitric oxide signaling system and to electrochemically assess the function of cardiac conduction system using canine isolated, blood-perfused heart preparation.
1. Development of the hypersensitive assay
1-1. Fluorometric assay of cGMP, which is important intracellular second messenger on the nitric oxide signalng system (Anal. Biochem., 1999).
1-2. Chemiluminescent assay of superoxide anion radicals, which are generated from the nitric oxide signaling system (Transplantation, 1999).
1-3. Chemiluminescent assay for hydroperoxide level of phosphatidylcholine hydroperoxide, which induce the conformat
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ional changes of cell membranes and cause the functional deterioration of receptors (J. Pharlnaceut. Biomed. Anal., 2000).
1-4. Myocardial interstitial norepinephrine measurement in the isolated, blood-perfused papillary muscle of dog using ex vivo microdialysis (J, Pharmacol. Toxicol. Methods, 2000). To know the myocardial interstitial norepinephrine concentration is important to assess the intracellular cAMP signaling system via β -adrenoceptors.
2. Electrochemical assessment of cardiac conduction system
2-1. We demonstrated that ONO-1 101 was a new ultrashort-acting β-adrenoceptor blocking drug by comparison with esmolol and propranolol using the canine isolated, blood-perfused heart preparations (J. Cardiovasc. Phanllacol., 1998)
2-2. By comparison of anti-M2 muscarinic effect of AF-DX 116 on atrioventricular nodal conduction with those of pirenzepine and atropine as antibradyarrhythmic drugs, we demonstrated that the muscarinic receptor subtype on the canine AV node is entirely of the M2-type, but only sparsely developed in the coronary vascular beds (J. Cardiovasc. Pharmacol., 1999).
2-3. By investigating the MCh-induced accentuated antagonism in the canine blood-perfused SA node, we demonstrated that MCh-induced accentuated antagonism in the SA node pacemaker activity can be modulated by endogeneous NO via an activation of the type II cyclic GMP-stimulated cyclic AMP phosphadiesterase (Am. J. Physiol., 2000). Less
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