甘氨酸和多粘菌素B拮抗内毒素活性及其机制的研究

Anti-endotoxic activity of glycine and polymyxin B and its mechanism

目的和方法： 通过ＬＡＬ 改良基质显色法和紫外光谱法观察甘氨酸／ 多粘菌素Ｂ（ＰＭＢ） 合剂体外拮抗内毒素的机制。结果：测定了各拮抗剂与内毒素中和后剩余内毒素的浓度（ 活性） ，结果表明甘氨酸／ＰＭＢ 合剂组、ＰＭＢ 组和甘氨酸组均显著低于内毒素组（ Ｐ＜ ０－０１） ，并且甘氨酸／ＰＭＢ 合剂组显著低于单独使用ＰＭＢ 组和甘氨酸组（ Ｐ＜ ０－０１） 。从紫外光谱图上可看到两种拮抗剂中和内毒素的作用是明显不同的：ＰＭＢ 可以降低内毒素的吸收峰值（２０６ ｎｍ 和２５７ｎｍ 处） ，而甘氨酸与内毒素的吸收峰值则相加（２１２ ｎｍ 和２５７ ｎｍ 处） 。结论： １） 内毒素脂质Ａ 上磷酸基团及相连的氨基葡萄糖双糖结构在甘氨酸、ＰＭＢ 作用下发生了变化，从而失去了对鲎试剂中Ｃ 因子的激活作用，并且甘氨酸、ＰＭＢ 联合应用比单独使用效果要好；２） 提示甘氨酸和ＰＭＢ 可能是分别作用在内毒素分子的不同结构部位。

AIM and METHOD: Modified Limulus Amebocyte Lysate (LAL)test with chromogenic substrate and ultraviolet spectrometer was used to investigate the mechanism of anti-endotoxin of glycine and polymyxin B in vitro RESULTS: Concentration of residual endotoxin(RE) was determined after antagonists neutralized endotoxin: In glycine/polymyxin B mixture group,polymyxin B group,glycine group RE were significantly lower than that of endotoxin group( P< 0 01), and in glycine/ polymyxin B mixture group RE was significantly lower than that of polymyxin B,glycine group( P< 0 01) Observed the graph of various groups with ultraviolet spectrometer, it was obvious that there were difference between action of two antagonists to neutralize endotoxin: polymyxin B decreased absorption peak value of endotoxin (at 206 nm and 257 nm), however, absorption peak values of glycine and endotoxin can be add up (at 212 nm and 257 nm) CONCLUSIONS: The result suggested that:1) phosphoric acid unit and amino-bio-glucose of lipid A was changed after endotoxin was neutralized by glycine,polymyxin B and lost the activating C factor in LAL, moreover, glycine/polymyxin B mixture might be better than any one of single antagonist; 2)glycine and polymyxin B affected different parts of endotoxin molecule