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.