大剂量补充肌酸抑制大鼠内源性肌酸合成的时间效应

Time Course Effects of High-dose Creatine Supplementation on Endogenous Creatine Biosynthesis in Rats

目的 :探讨大剂量补充肌酸抑制大鼠内源性肌酸合成和影响代谢的时间效应。方法 :大剂量补充肌酸 (3 0g/kg/d)不同时间后 ,测定大鼠肾脏和胰脏精氨酸 -甘氨酸脒基转移酶 (AGAT)活性、酶促反应产物胍乙酸含量、血清和骨骼肌的肌酸含量和肌酸激酶活性、血清肌酐水平 ,分析补充肌酸的时间 -效应关系。结果 :补充大剂量肌酸 4天后 ,大鼠腓肠肌湿重下降 ;大剂量补充肌酸可在 12小时抑制肾脏和胰脏的AGAT活性 ,使胍乙酸生成量明显减少。补充肌酸 0 5～ 1天内 ,A GAT活性下降幅度最大 ;补充时间越长 ,AGAT活性抑制越明显 ,胍乙酸生成越少。大剂量补充肌酸可引起大鼠腓肠肌和血清肌酸含量增加 ,腓肠肌CK活性出现升高趋势 ,还引起血清肌酐水平呈快速而短暂的升高。结论 :大剂量补充肌酸可在短时间内对自身肌酸合成体系造成抑制。

Objective The purpose of this study was to research the time cour se effects of creatine supplementation with high doses on the endogenous biosynt hesis and metabolism of creatine in rats. Methods After treate d with high-dose creatine in different durations, the activities of L-arginine:glycine amidinot ransferase (AGAT) and the contents of guanidinoacetic acid (GA) in kidney and pa ncreas, creatine concentrations and creatine kinase (CK) activities in skeletal muscles and serum, and creatinin e levels in serum were determined. Results After administratio n of creatine at high dose of 3.0g/kg for four days, the wet weight of the rat gastrocnemius we re lightened. The activities of AGAT in kidney and pancreas were inhibited in 12 hours after creatine supplementation; consequently GA contents in kidney were d ecreased markedly. Within 12 to 24 hours after creatine supple mentation, the activities of AGAT in kidney and pancreas dropped quickly. The lo nger the creatine was taken, the lower AGAT activities and the less GA contents were. Wit h high-dose creatine supplement, the creatine contents in gastrocnemius and seru m were raised gradually and CK activity in gastrocnemius showed an increasing te ndency. A temporary significant increase (P<0.01) in serum creatinine concen tration was also found. Conclusion The endogenous biosynthesis of creatine in rats could be inhibited in a short period of time after a high d ose of creatine supplementation.