门静脉血氨对猪肝尿素循环和糖异生的影响

Effect of Portal Ammonia on Urea Cycle and Gluconeogenesis in Liver of Pig

旨在探索门静脉血氨对猪肝尿素循环和糖异生的影响。试验选取体重约20kg的杜长大仔猪8头,随机分成2组,每组4头,安装门静脉-肝静脉插管,分别灌注65和35mmol·L-1的氯化铵(NH4Cl),采集肝静脉血液,利用气相色谱-质谱联用技术分析血清代谢产物,同时测定肝组织尿素循环和糖异生相关酶基因表达及活性。结果表明,门静脉灌注高浓度的NH4Cl显著提高了血液中尿素、葡萄糖和葡萄糖6磷酸的含量(P<0.05),显著降低了血液中丙氨酸、谷氨酸、天冬氨酸的含量(P<0.05);高浓度的NH4Cl还显著上调了氨甲酰磷酸合成酶1(CPS1)、鸟氨酸转氨甲酰磷酸酶(OTC)、精氨酸酶1(Arg1)、磷酸烯醇式丙酮酸羧激酶(PCK)和葡萄糖6磷酸酶(G6PC)的基因表达(P<0.05),同时相应酶活性分别提高了50.77%、44.47%、41.24%、46.99%、54.57%(P<0.05)。结果提示,随着肝氨负荷的增加,尿素循环加强,诱导丙氨酸、天冬氨酸和谷氨酸等氨基酸代谢为尿素提供额外的氮源,生成的碳骨架用于肝糖异生。

This experiment was conducted to study the effect of portal ammonia on urea cycle and gluconeogenesis in liver of pig.Eight pigs（Duroc×Landrace×Yorkshire）,with the average weight of 20 kg,were randomly assigned to two treatments with 4pigs in each treatment.Pigs were surgically implanted with catheter in the portal vein and hepatic vein.Then 65 and 35mmol·L-1 of ammonium chloride（NH4Cl）were infused into liver by portal catheter.Serum samples were collected to analyze metabolites based on gas chromatography-mass spectrometry metabolomics.Liver samples were collected to examine gene expression and enzyme activity in urea cycle and gluconeogenesis.The results showed that,compared with low concentration NH4 Cl,the infusion of high concentration NH4 Cl significantly increased the content of urea,glucose and glucose-6-phosphate（P〈0.05）,the content of alanine,glutamate and aspartate were significantly decreased（P〈0.05）;addtionally,high concentration NH4 Cl significantly upregulated the expression of carbamoyl-phosphate synthase 1（CPS1）,ornithine carbamoyl-transferase（OTC）,arginase 1（Arg1）,phosphoenolpyruvate carboxykinase（PCK）and glucose-6-phosphatase（G6PC）,meanwhile the corresponding enzyme activities increased 50.77%,44.47%,41.24%,46.99% and 54.57%（P〈0.05）,respectively.These results indicated that,with the ammonia load increased into liver,the urea cycle was increased and the additional nitrogen was supplied by amino acid metabolism（alanine,aspartate,glutamate）,of which the carbon skeleton were used for hepatic gluconeogenesis.