Headrick J, Willis R J
School of Science, Griffith University, Queensland, Australia.
Pflugers Arch. 1989 Feb;413(4):354-8. doi: 10.1007/BF00584483.
This study examines the possibility that endogenous adenosine modulates efficiency in isovolumic perfused rat hearts stimulated with isoproterenol or norepinephrine. Efficiency in these hearts is calculated as the rate of pressure work divided by the myocardial oxygen consumption. Within 2 min of infusion of isoproterenol (50 nM), heart rate increased by 35%, the rate pressure product by 290%, oxygen consumption by 142%, and efficiency by 67%. Infusion of adenosine deaminase (2-4 IU/ml), or 8-phenyltheophylline (5 microM), into stimulated hearts augmented the increase in heart rate by 40-45%, rate-pressure product by 18-20%, and oxygen consumption by 50-55%. Efficiency was reduced by 30-35%. Adenosine release into the coronary venous effluent increased from 195 +/- 20 pmol/min/g to 2400 +/- 180 pmol/min/g after 5 min. A similar pattern of results was observed when norepinephrine (0.1 mM) was used. The results indicate that extracellular adenosine, released by catecholamine treatment, inhibits the effects of the catecholamines on rate and contractility. Consequently, adenosine reduces cardiac work (rate-pressure product), but in so doing, improves efficiency.
本研究探讨内源性腺苷是否能调节异丙肾上腺素或去甲肾上腺素刺激下的等容灌注大鼠心脏的效率。这些心脏的效率计算为压力功速率除以心肌耗氧量。在输注异丙肾上腺素（50 nM）的2分钟内，心率增加35%，心率压力乘积增加290%，耗氧量增加142%，效率增加67%。向受刺激的心脏输注腺苷脱氨酶（2 - 4 IU/ml）或8 - 苯基茶碱（5 microM），可使心率增加幅度提高40 - 45%，心率压力乘积提高18 - 20%，耗氧量提高50 - 55%。效率降低30 - 35%。5分钟后，冠状动脉流出液中的腺苷释放量从195±20 pmol/min/g增加到2400±180 pmol/min/g。使用去甲肾上腺素（0.1 mM）时观察到类似的结果模式。结果表明，儿茶酚胺处理释放的细胞外腺苷抑制了儿茶酚胺对心率和收缩性的影响。因此，腺苷减少了心脏做功（心率压力乘积），但这样做却提高了效率。
