Newby A C, Worku Y, Holmquist C A
Adv Myocardiol. 1985;6:273-84.
The increase in tissue and coronary effluent adenosine concentration in hearts undergoing net ATP breakdown results from an accelation of adenosine formation and not from an inhibition of adenosine inactivation. Adenosine formation takes place inside intact isolated cells by a pathway distinct from the cell membrane 5'-nucleotidase, which hydrolyzes only extracellular AMP. Both the magnitude and the variation in the rate of adenosine formation in polymorphonuclear leukocytes undergoing ATP catabolism can be accounted for by the properties of a cytosolic 5'-nucleotidase that is also present in heart. This enzyme, which is allosterically activated by ATP-Mg and inhibited by Pi, provides a direct biochemical link between the energy status of the cell and the rate of adenosine formation. The actions of adenosine to dilate coronary arterioles, antagonize the inotropic effect of catecholamines, and reduce sympathetic-nerve firing would ameliorate the original energy imbalance. Adenosine may therefore function in heart and also in brain, skeletal muscle, kidney, and adipose tissue as a "retaliatory metabolite" that protects the cell against excessive external stimulation.
在经历净ATP分解的心脏中，组织和冠状动脉流出液中腺苷浓度的增加是由于腺苷生成加速，而非腺苷失活受到抑制。腺苷的生成在完整的分离细胞内通过一条不同于细胞膜5'-核苷酸酶的途径进行，后者仅水解细胞外的AMP。正在进行ATP分解代谢的多形核白细胞中腺苷生成速率的大小和变化，都可以用心脏中也存在的一种胞质5'-核苷酸酶的特性来解释。这种酶受ATP-Mg变构激活，受Pi抑制，它在细胞的能量状态和腺苷生成速率之间提供了直接的生化联系。腺苷使冠状动脉小动脉扩张、拮抗儿茶酚胺的变力作用以及减少交感神经放电的作用，会改善最初的能量失衡。因此，腺苷可能在心脏以及脑、骨骼肌、肾脏和脂肪组织中作为一种“报复性代谢物”发挥作用，保护细胞免受过度的外部刺激。
