内毒素休克新生大鼠肾组织内NO对第二信使的调节作用

Regulation of NO on cAMP and cGMP in kidneys of neonatal rats with endotoxic shock

目的探讨新生大鼠内毒素(LPS)休克时肾组织内一氧化氮(NO)对环磷酸腺苷和环磷酸鸟苷(cAMP,cGMP)第二信使的调节作用.方法7日龄新生大鼠180只,分为3组.对照组(A组):腹腔注入0.1ml生理盐水;LPS组(B组):腹腔注射LPS 5 mg/kg;地塞米松组(Dex,C组):LPS 5 mg/kg+Dex10mg/kg;采用硝酸还原酶法测定肾组织NO,放免法检测肾组织cAMP及cGMP浓度,动态观察0,2,4,6及24 h血气及各项指标变化和24h动物死亡率.结果B组NO于自2h起显著高于A组各点(P＜0.05～P＜0.01);C组NO 2 h也明显高于A和B组(P＜0.05),至24 h低于B组(P＜0.05),与A组无差异;B组cAMP和cGMP自2 h起显著高于A组各点(P＜0.05～P＜0.01);C组cAMP 2～24h均高于A和B两组各值(均P＜0.01),cGMP于2 h高于A和B两组各值(P＜0.01),至24 h显著低于B组(P＜0.01);B组24 h血气呈现显著代谢性酸中毒,呼吸性硷中毒伴低氧血症.24h死亡率B组为50%,C组20%,两组差异显著(P＜0.05).结论新生大鼠内毒素休克时肾脏合成过量的NO,肾脏cAMP,cGMP浓度均显著升高,伴随机体内环境紊乱和死亡率增加.Dex通过抑制肾脏NO的合成而调节第二信使信号系统,降低死亡率。

Objective: To observe the regulating effects of NO on cyclic adenosine monophosphate and cyclic guanosine 3, 5-monophosphate (cAMP, cGMP) in kidneys of neonatal rats with endotoxic shock. Methods: 180 seven-day newborn Wistar rats were randomly divided into 3 groups. Group A (control group): animals were injected intraperitoneally with the same volume (0.1ml) of 0.9% sodium chloride as the other 2 groups. Group B (LPS group): animals were injected by a single bolus of lipopolysaccharide (LPS 5 mg/kg). Group C (Dex group): animals received LPS 5 mg/kg+Dxe10 mg/kg. At the designed time point (0, 2, 4, 6, 24 h) ten newborn rats were killed and kidneys were collected for assay. The content of NO in kidneys were measured by colorimetric analysis. The levels of cAMP and cGMP were measured by radioimmunoassay. Blood gas analysis was dynamicly observed and mortality of rats at 24-hour in each group was recorded. Results: In group B, the concentration of NO, cAMP and cGMP of the kidneys were all higher than that of group A from 2 hours to 24 hours (P <0.01); in group C, the concentration of NO was also higher than that of group A at 2 hours (P <0.05), but the value was lower than group B at 24 hours(P <0.05); the content of cAMP was also higher than that of group A and B from 2 hours to 24 hours (P <0.01), the cGMP value peaks at 2 hours (P <0.01), and then gradually decreased to the lower level than the group B at 24 hours (P <0.01); Blood gas analysis showed metabolic acidosis with respiratory alkalosis and hypoxycemia in the rats of endotoxic shock at 24 hours. Mortality of group B was higher than that of group A at 24 hours (50%, 30%, P <0.05). Conclusions: The study suggests that LPS stimulate the newborn rat kidneys to create excessive NO and more cAMP and cGMP, giving rise to abnormality of blood gas analysis and higher mortality of newborn rat with endotoxic shock. Dex can protect kidneys from damage by regulating the NO- second messenger system in endotoxic shock of neonates, and reduce the mortality.