Pridjian A K, Bove E L, Bolling S F, Childs K F, Brosamer K M, Lupinetti F M
Department of Surgery, University of Michigan School of Medicine, Ann Arbor.
J Thorac Cardiovasc Surg. 1994 Feb;107(2):520-6.
Age-related differences in the activity of 5'-nucleotidase, an enzyme responsible for conversion of high-energy phosphates to their the diffusible precursors, may help to explain age-related differences in tolerance of global myocardial ischemia. Postischemic function and high-energy phosphate content were measured in the hearts of rabbits 7 to 10 days old (neonate), 30 to 40 days old (1 month), and 6 to 12 months old (adult). Hearts in each age group were subjected to 60 minutes of ischemia at 34 degrees C either with no cardioplegia, with unmodified St. Thomas' Hospital cardioplegic solution, or with St. Thomas' Hospital cardioplegic solution with pentoxifylline, a 5'-nucleotidase inhibitor. These groups were compared with one another and with control hearts that were continuously perfused for 1 hour. In adults, addition of pentoxifylline to St. Thomas' Hospital cardioplegic solution restored adenosine triphosphate and total nondiffusible nucleotide levels to control values and improved recovery of cardiac output and developed pressure compared with results with unmodified St. Thomas' Hospital cardioplegic solution. In contrast, biochemical and functional parameters in neonatal hearts were not affected by either unmodified St. Thomas' Hospital cardioplegic solution cardioplegia or St. Thomas' Hospital cardioplegic solution with pentoxifylline. Functional recovery in neonatal hearts subjected to unprotected ischemia was superior to that in the older age groups. In 1-month-old hearts, St. Thomas' Hospital cardioplegia improved recovery compared with recovery after unprotected ischemia, but no incremental improvement in function or high-energy stores was seen with addition of pentoxifylline. The lack of effect of pentoxifylline on neonatal hearts suggest that there is a relative deficiency of 5'-nucleotidase in this age group. This may contribute to the improved functional recovery observed in unprotected hearts. Furthermore, addition of pentoxifylline to adult hearts appears to confer the benefits of low 5'-nucleotidase activity occurring naturally in the neonate.
5'-核苷酸酶负责将高能磷酸盐转化为可扩散的前体，其活性的年龄相关差异可能有助于解释全球心肌缺血耐受性的年龄相关差异。对7至10日龄（新生儿）、30至40日龄（1个月）和6至12月龄（成年）兔子的心脏进行缺血后功能和高能磷酸盐含量的测量。每个年龄组的心脏在34摄氏度下进行60分钟的缺血，分别采用无心脏停搏液、未改良的圣托马斯医院心脏停搏液或添加己酮可可碱（一种5'-核苷酸酶抑制剂）的圣托马斯医院心脏停搏液。将这些组相互比较，并与持续灌注1小时的对照心脏进行比较。在成年组中，与未改良的圣托马斯医院心脏停搏液相比，向圣托马斯医院心脏停搏液中添加己酮可可碱可使三磷酸腺苷和总不可扩散核苷酸水平恢复到对照值，并改善心输出量和舒张期压力的恢复。相比之下，未改良的圣托马斯医院心脏停搏液或添加己酮可可碱的圣托马斯医院心脏停搏液均未影响新生心脏的生化和功能参数。未受保护缺血的新生心脏的功能恢复优于老年组。在1月龄的心脏中，与未受保护缺血后的恢复相比，圣托马斯医院心脏停搏液改善了恢复，但添加己酮可可碱并未使功能或高能储备有进一步改善。己酮可可碱对新生心脏无效表明该年龄组中5'-核苷酸酶相对缺乏。这可能有助于未受保护心脏中观察到的功能恢复改善。此外，向成年心脏中添加己酮可可碱似乎赋予了新生儿自然存在的低5'-核苷酸酶活性的益处。
