过量蛋氨酸对大鼠肝,脑组织^3H—亮氨酸掺入量的影响

EFFE CT OF EXCESS DIETARY METHIONINE ON ~3H- LEUCINE INCORPORATION OF HEPATIC AND BRAIN TISSUE IN RATS

本实验以~3H-亮氨酸示踪,研究了过量蛋氨酸对大鼠肝、脑组织蛋白质合成代谢的影响。 以米为主食,补充小量黄豆粉配制成含12％蛋白质的基本饲料。实验分三组,以基本饲料添加0.2％DL-蛋氧酸为对照组;基本饲料添加2.0％DL-蛋氨酸组以及添加2.0％DL-蛋氨酸和3.0％甘氨酸为两个实验组。每组大鼠18只,单笼饲养21天。 结果表明,注入标记亮氨酸1～10h,添加过量蛋氨酸组大鼠肝组织~3H-亮氨酸掺入量(dpm/mg肝)明显低于对照组(P【0.01),掺入高峰时间延迟出现。添加过量蛋氨酸和3.0％甘氨酸组,~3H-亮氨酸掺入量比单纯添加过量蛋氨酸组明显提高(P【0.05),但仍低于对照组,掺入高峰与对照组相同在第2h出现。相反,三组大鼠脑组织1～10h内~3H-亮氨酸掺入量与掺入高峰时间均未见明显差别(P】0.1)。提示过量蛋氨酸的毒性对器官蛋白质合成的作用是不一致的。

Fifty four male Wistar rats weighing 60-90g were divided into three groups of 18 each; rice-soybean basal diet with 0.2%DL-methionine as control, 2.0%D1-methionine supplemented group, 2.0%DL-methionine and 3.0%glycine supplemented group. All animals were housed in individual wire cages and both experimental diet and water were given ad libitum. After feeding 21 days, 0.037MBq/g bw of 3H-leucine was injected intraperitoneally. At 1,2, 4, 6, 8, 10 hours after injection, three rats per group were killed and the radioactivity of 3H-leucine per mg hepatic and brain tissue (dpm/mg tissue) were determined by liquid scintillation counter. The results showed that 3H-leuciue incorporarted during the entire 10 hours period of observation markedly declined and its peak was delayed in the hepatic tissue of excessive methionine supplemented group. However, 3H-leucine incorporated was improved significantly in liver in the rats fed excessive DL-methionine with glycine diet. In contrast, no significant difference of incorporation in the rat brain among the three groups were found. The results demonstrated that the addition of excess methionine retarded evidently protein synthesis of hepatocytes in the rats, but no similar toxic effect occurred in the rat brain tissue.