Savabi F
Department of Pharmacology and Nutrition, University of Southern California School of Medicine, Los Angeles 90033.
Proc Natl Acad Sci U S A. 1988 Oct;85(20):7476-80. doi: 10.1073/pnas.85.20.7476.
To measure the actual percentage of intracellular free creatine participating in the process of energy transport, the incorporation of [1-14C]creatine into the "free" creatine and phosphocreatine (PCr) pools in spontaneously beating isolated rat atria, under various conditions, was examined. The atria were subjected to three consecutive periods, control, anoxia, and postanoxic recovery, in medium containing tracers of [1-14C]creatine. The tissue content and specific activity of creatine and PCr were determined at the end of each period. The higher specific activity found for tissue PCr (1.87 times) than creatine, independent of the percentage of total intracellular creatine that was present as free creatine, provides evidence for the existence of two separate pools of free creatine. Analysis of the data shows that in the normal oxygenated state approximately equal to 9% of the total intracellular creatine is actually free to participate in the process of energy transport (shuttle pool). About 36% of the total creatine is bound to unknown intracellular components and the rest exists as PCr. The creatine that was taken up and the creatine that was released from the breakdown of PCr have much greater access to the site of phosphorylation than the rest of the intracellular creatine. A sharp increase in the specific activity of residual PCr on prolongation of anoxic time was also observed. This provides evidence for a nonhomogeneous pool of PCr, for the most recently formed (radioactive) PCr appeared to be hydrolyzed last.
为了测量参与能量转运过程的细胞内游离肌酸的实际百分比，研究了在各种条件下，[1-¹⁴C]肌酸掺入自发搏动的离体大鼠心房中“游离”肌酸和磷酸肌酸（PCr）池的情况。心房在含有[1-¹⁴C]肌酸示踪剂的培养基中经历三个连续阶段：对照、缺氧和缺氧后恢复。在每个阶段结束时测定肌酸和PCr的组织含量及比活性。发现组织PCr的比活性（1.87倍）高于肌酸，且与作为游离肌酸存在的细胞内总肌酸百分比无关，这为存在两个独立的游离肌酸池提供了证据。数据分析表明，在正常氧合状态下，约9%的细胞内总肌酸实际上可自由参与能量转运过程（穿梭池）。约36%的总肌酸与未知细胞内成分结合，其余以PCr形式存在。摄取的肌酸和从PCr分解中释放的肌酸比细胞内其余肌酸更容易进入磷酸化位点。还观察到缺氧时间延长时残余PCr的比活性急剧增加。这为PCr池的非均一性提供了证据，因为最新形成的（放射性）PCr似乎最后被水解。
