^13碳核磁共振波谱学检测烧伤大鼠肝脏细胞合成功能的变化

目的 建立安全、特异的^13碳核磁共振(^13C NMR)波谱学方法，观察严重烧伤大鼠肝脏细胞糖原异生和回补反应等合成代谢功能的变化。方法 成年SD大鼠在吸入麻醉下行左颈动脉和右颈外静脉插管后，随机分成40％TBSAⅢ度烫伤组(B组)和假烫伤对照组(C组)。B组伤后20min开始液体复苏，伤后72h静脉持续滴注示踪剂[1、2、3-^13C]-丙酸钠(SP)，并于滴注45和60min时分别检测血浆和肝脏^13C NMR波谱、动脉血压、心率、血糖和血钠水平，运用输入-输出三羧酸循环的数学模型计算代谢参数。结果烧伤后72hB组动脉血压仍低于C组，血糖与C组比较无明显差异；SP对平均动脉压、心率和血钠均无影响；血糖^13C同位素标记形式与肝糖一致；持续滴注SP45min时SP即可达到代谢稳定状态；B组肝脏细胞糖原异生、回补反应和丙酮酸循环的碳流量均较C组明显增强，而三羧酸循环碳流量相对减少；肝脏丙氨酸、谷氨酸和谷氨酰胺池也明显扩大。结论 静脉注射SP不改变平均动脉压、心率和血钠，静脉滴注示踪剂45min即能达到代谢稳态，血糖^13C标记形式可代表肝糖的^13C标记形式；大面积烧伤后72h，肝脏回补反应、糖原异生和丙酮酸循环均增强，但外周组织血糖的利用率也相应提高。

Alterations of anabolism in hepatic cells of burned rats measured by (13)C NMR spectroscopy]

OBJECTIVE: To introduce a safe and specific approach of (13)C NMR spectroscopy and investigate the alterations in hepatic anabolism functions including pyruvate recycling, gluconeogenesis and anaplerosis in severely burned rats. METHODS: Adult Spreque -- Dawley (SD) rats were catheterized arteriovenously via left carotid and right external jugular vein under inhalation anesthesia and were randomly divided into burn group (B) and sham burn group (S). Fluid resuscitation started 20 min postburn. Sodium [1, 2, 3 -- (13)C] propionate (SP) was intravenously administered as a tracer at 72 postburn hour (PBH). (13)C NMR spectroscopy of extracted plasma and liver, arterial blood pressure, heart rate and plasma glucose and sodium levels were measured. Metabolic parameters were calculated using a mathematical model of input -- output matrix to feed the tricarboxylic acid cycle. RESULTS: When compared to those in C group, burned rats exhibited a lower arterial blood pressure, but normal blood glucose at 72 PBH. Intravenous SP infusion did not alter MAP, heart rate and plasma sodium. The form of blood sugar labeled by (13)C isotopomer was in excellent agreement with that from liver. After continuous infusion of SP for 45 mins, SP could reach metabolic steady status. The hepatic cellular gluconeogenesis, anaplerosis and the carbon flow rate in pyruvate recycling significantly increased in B group when comparing to those in C group. But the carbon flow rate in Kreb's cycle decreased relatively, and hepatic pools of alanine, glutamic acid and glutamine were enlarged obviously in burned rats relative to sham burn group. CONCLUSION: These data suggested that intravenous infusion of SP would not alter MAP, heart rate and blood sodium. Forty -- five mins after the intravenous infusion, the tracer could reach metabolic steady status. The form of blood sugar labeled by (13)C could represent that of hepatic sugar. Seventy -- two hours after major burns, there were increased hepatic anaplerosis, gluconeogenesis and pyruvate recycling and a correspondent increased utilization ratio of blood sugar by peripheral tissue.