Effect of palmitate or lipid emulsion on nitrogen metabolism during hyperthermic perfusion of rat liver

Livers of fasted rats were perfused for one hour at 37 degrees or 42 degrees. Endogenous hepatic ureogenesis was increased twofold at 42 degrees and the release of endogenous ninhydrin-reactive amino nitrogen was not changed by hyperthermia. Exogenous amino acids at 10 times the normal plasma concentration stimulated hepatic ureogenesis sevenfold at 37 degrees and over twofold at 42 degrees. Exogenous amino acids stimulated hepatic amino acid uptake at 37 degrees. Uptake of the exogenous amino acids at 42 degrees was about 40% of that observed at 37 degrees. However, exogenous amino acid uptake in the presence of 1 mM palmitate was not altered at 42 degrees. Ureogenesis in the presence of supplemental amino acids and palmitate was significantly reduced at 37 degrees and moderately reduced at 42 degrees, suggesting decreased amino acid catabolism. Ten percent Intralipid, a clinically available lipid emulsion primarily consisting of triglycerides in a physical form similar to chylomicrons at a perfusate concentration of 1 ml/100 ml, did not markedly alter hepatic ureogenesis or amino acid dynamics at 37 degrees or 42 degrees in the presence or absence of amino acids. It is concluded that palmitate blocks the adverse effect of hyperthermia on hepatic amino acid uptake.