Fry D M, Morales M F
J Cell Biol. 1980 Feb;84(2):294-7. doi: 10.1083/jcb.84.2.294.
Experiments designed to test the hypothesis that intracellular creatine level regulates the synthesis of muscle specific proteins have failed to demonstrate any creatine regulatory effect. Manipulation of the extracellular creatine in culture medium over a 5,700-fold range (1.3-7.4 mM) was successful in altering intracellular total creatine by only a factor of 20 (1.4-42 mg creatine/mg protein), an indication that muscle cells are able to regulate intracellular creatine levels over a wide range of external creatine concentrations. Alterations of cell creatine had no effect on either total protein synthesis or synthesis of myosin heavy chain. Methods were perfected to measure total creatine, and incorporation of [3H]leucine into total protein and purified myosin heavy chain from the same culture dish to avoid the possibility of variation between dishes. The creatine analog 1-carboxymethyl-2-iminohexahydropyrimidine (CMIP) previously reported to stimulate myosin synthesis in culture was found to depress creatine accumulation by cells and depressed total protein synthesis and synthesis of myosin heavy chain. This inhibitory action of CMIP is consistent with the reported competitive inhibition of creatine kinase and presumed interference with energy metabolism.
旨在验证细胞内肌酸水平调节肌肉特异性蛋白质合成这一假说的实验未能证明肌酸有任何调节作用。在培养基中对细胞外肌酸进行5700倍范围（1.3 - 7.4 mM）的操作，仅成功使细胞内总肌酸改变了20倍（1.4 - 42 mg肌酸/ mg蛋白质），这表明肌肉细胞能够在广泛的细胞外肌酸浓度范围内调节细胞内肌酸水平。细胞肌酸的改变对总蛋白质合成或肌球蛋白重链合成均无影响。完善了测量总肌酸以及从同一培养皿中测量[3H]亮氨酸掺入总蛋白质和纯化的肌球蛋白重链的方法，以避免不同培养皿之间出现差异的可能性。先前报道可在培养中刺激肌球蛋白合成的肌酸类似物1 - 羧甲基 - 2 - 亚氨基六氢嘧啶（CMIP），被发现会抑制细胞的肌酸积累，并抑制总蛋白质合成和肌球蛋白重链合成。CMIP的这种抑制作用与报道的对肌酸激酶的竞争性抑制以及推测的对能量代谢的干扰一致。
