淀粉样β蛋白对大鼠脑细胞内三磷酸肌醇的影响

Effects of beta-amyloid protein on inositol trisphosphate in brain cells of rats

目的:观察淀粉样β蛋白对大鼠脑肌醇1,4,5-三磷酸含量的影响,通过磷脂酰肌醇代谢的变化,进一步探讨淀粉样β蛋白的神经毒性机制,方法:实验于2004-04/09在中国医科大学药理学及生理学实验室进行,取Wistar成年雄性大鼠10只,随机分为模型组和生理盐水两组各5只。模型组双侧脑室各注射淀粉样β蛋白1～425μL(各30nmol);生理盐水组注射5μL的生理盐水。所有大鼠常规方法饲养1周后麻醉状态下处死取脑皮质,测定两组大鼠脑组织肌醇1,4,5-三磷酸含量基础值,并观察M受体激动剂卡巴胆碱(1mmol/L)及KCl(40mmol/L)对肌醇1,4,5-三磷酸生物合成的影响。结果:10只大鼠均进入进入结果分析。①模型组大鼠脑组织基础肌醇1,4,5-三磷酸含量显著低于生理盐水组(6.7±2.2),(12.0±1.4)nmol/g,P<0.01。②脑组织经1mmol/L卡巴胆碱作用后肌醇1,4,5-三磷酸的产生两组均增加,120s时达高峰,但模型组明显低于对照组(P=0.00788)。③40mmol/LKCl作用后两组大鼠脑组织肌醇1,4,5-三磷酸的产生均增加,30s时达高峰,但模型组明显低于对照组(P=0.000324)。结论:①淀粉样β蛋白降低基础肌醇1,4,5-三磷酸的含量,并能抑制卡巴胆碱及KCl诱发的肌醇1,4,5-三磷酸的生物合成。②淀粉样β蛋白抑制肌醇1,4,5-三磷酸的合成与损害G蛋白-磷脂酶C偶联和磷酯酰肌醇4,5-二磷酸敏感的磷脂酶C均有关。

AIM： To observe the influence of β-amyloid protein on the contents of inositol 1, 4, 5-trisphosphate in brain of rats, and further study the neurotoxic mechanism of β-amyloid protein based on the metabolic changes of phosphoinositide. METHODS： The experiment was done in the pharmacological and physiological labs of China Medical University between April and September 2004. Ten adult male Wistar rats were randomly divided into model group （n=5） and saline group （n=5）. Rats in the model group were treated with bilateral ventricular injection of 5μL β-amyloid protein 1-42 （30 nmol respectively）, and those in the saline group were injected with saline of the same volume. One week after regular feed, all the rats were killed under anesthesia and cerebral cortex was taken, and the basal contents of inositol 1, 4, 5-trisphosphate in brain of rats were detected, and the effects of carbachol （1 mmol/L）, KCI （40 mmol/L） on the synthesis of inositol 1, 4, 5- trisphosphate were observed. RESULTS： All the 10 rats were involved in the analysis of results. ① The basal basal contents of inositol 1, 4, 5-trisphosphate in brain tissues were significantly lower in the model group than in the control group [（6.7±2.2）, （12.0±1.4） nmol/g, P 〈 0.01].②After brain tissue was treated with 1 mmol/L carbachol, the inositol 1, 4, 5-trisphosphate increased and reached the peak at 120 s, but it was significantly lower in the model group than in the control group （P = 0.007 88）.③ While treated with 40 mmol/L KCl, the inositol 1, 4, 5-trisphosphate increased and reached peak at 30 s in both groups, but it was obviously lower in the model group than in the control group （P = 0.000 324）. CONCLUSION： ①β-amyloid protein can reduce basal contents of inositol 1, 4, 5-trisphosphate and inhibit carbachol and KCl-induced synthesis of inositol 1, 4, 5-trisphosphate.② The mechanism of the inhibition by β- amyloid protein is associated with the damage of the linkage between G protein and phospholipase C and the inositol 4, 5-trisphosphate sensitive phospholipase C.