Hohl C M
Department of Medical Biochemistry, Ohio State University, Columbus, Ohio 43210, USA.
Am J Physiol. 1999 May;276(5):H1502-10. doi: 10.1152/ajpheart.1999.276.5.H1502.
The purpose of this study was to examine in situ regulation of AMP deaminase in newborn piglet cardiac myocytes and to determine its role in nucleotide metabolism during ischemia. When a rapid deenergization paradigm was used to assay AMP deaminase, enzyme activity depended on the hormonal and metabolic status of cells just before deenergization. Inosine 5'-monophosphate (IMP) formation was increased 150% in deenergized myocytes pretreated with phorbol 12-myristate 13-acetate (PMA; EC50 = 4.7 x 10(-8) M). This effect was 90% blocked with the protein kinase C (PKC) inhibitor staurosporine. In addition, the beta-adrenergic agonist isoproterenol stimulated AMP deaminase activity (EC50 = 1.5 x 10(-8) M), and IMP formation was directly correlated to intracellular cAMP levels (r2 = 0.9). Furthermore, adenosine increased IMP formation, whereas nonrespiring, glycolyzing piglet myocytes had reduced AMP deaminase activity. Pretreatment of perfused piglet hearts with adenosine, but not PMA, before exposure to global ischemia resulted in enhanced conversion of AMP to IMP during the ischemic period. Similar results were obtained in piglet myocytes preincubated with adenosine or PMA before exposure to simulated ischemia. These results may be relevant to the preconditioning phenomenon.
本研究的目的是检测新生仔猪心肌细胞中AMP脱氨酶的原位调节，并确定其在缺血期间核苷酸代谢中的作用。当使用快速去能模式检测AMP脱氨酶时，酶活性取决于去能前细胞的激素和代谢状态。用佛波酯12-肉豆蔻酸酯13-乙酸酯（PMA；EC50 = 4.7×10^(-8) M）预处理的去能心肌细胞中，5'-肌苷单磷酸（IMP）的形成增加了150%。蛋白激酶C（PKC）抑制剂星形孢菌素可阻断90%的这种效应。此外，β-肾上腺素能激动剂异丙肾上腺素刺激AMP脱氨酶活性（EC50 = 1.5×10^(-8) M），IMP的形成与细胞内cAMP水平直接相关（r2 = 0.9）。此外，腺苷增加IMP的形成，而不进行呼吸、进行糖酵解的仔猪心肌细胞的AMP脱氨酶活性降低。在暴露于全心缺血之前，用腺苷而非PMA预处理灌注的仔猪心脏，导致缺血期间AMP向IMP的转化增强。在暴露于模拟缺血之前，用腺苷或PMA预孵育的仔猪心肌细胞也获得了类似的结果。这些结果可能与预处理现象有关。
