- 作者: Wen-Pin chen Ming-Jai Su
- 作者服務機構: Pharmacological Institute, college of Medicine, National taiwan University, Taipei, Taiwan, ROC
- 中文摘要: --
- 英文摘要: Alterations in -adrenoceptor ( AR) density and relatedsignal transduction proteins were reported in cardio-myopathic hearts in the failing stage. The electrome-chanical modification of -adrenergic stimulation in thefailing heart is unclear. The present study compares the AR-stimulated electromechanical response in failingventricles of genetically cardiomyopathic BIO 14.6 ham-sters (280-320 days old) with that in age-matched normalSyrian hamsters. The action potential was recorded witha conventional microelectrode technique, and twitchforce was measured with a transducer. In the presence ofpropranolol, phenylephrine increased the contractionand prolonged the action potential duration (APD) tosimilar values in ventricles of both strains, despite a pro-longed basal APD in cardiomyopathic ventricles. Thepositive inotropism stimulated by phenylephrine wasinhibited by staurosporine, and was potentiated by 4 -phorbol-12,13-dibutyrate (PDBu) in both strains. Themaximum positive inotropic effect of phenylephrine inPDBu-treated ventricles of normal hamsters was signifi-cantly greater than that in BIO 14.6 hamsters. The effectsof phenylephrine on the ventricular force-frequency rela-tionship and on the mechanical restitution in both nor-mal and BlO 14.6 strain hamsters were examined. Theuniform negative force-frequency relationship and thealtered mechanical restitution reveala defect of intracel-lular Ca handling in cardiomyopathic BIO 14.6 ham-sters. -Adrenergic modulation cannot convert the de-fective properties in the model of the failing heart. Nev-ertheless, phenylephrine decreased postrest potentia-tion in short rest periods, and enhanced postrest decayafter longer resting periods. The results indicate that -adrenergic action enhances a gradual loss of Ca fromthe sarcoplasmic reticulum, although its action in pro-longing the APD can indirectly increase the influx ofCa .
- 中文關鍵字: --
- 英文關鍵字: Adrenoceptor. Phenylephrine. Protein kingase C. Cardiomyopathic BIo 14.6 hamster