Metabolic response of simultaneous versus sequential intravenous administration of amino acids and energy substrates to rats.

Three groups of rats were maintained on total intravenous nutrition for ten days. Group SA and SB were infused sequentially (2 X 12 h periods per day), SA received amino acids (AA) during the night and carbohydrates (CHO) + FAT during the day. The SB group received nutrients in the opposite order. A control group received a mixed solution simultaneously for 24 h/day. The sequentially fed groups showed a lower weight gain (2.4 +/- 0.4, 2.6 +/- 0.2 vs 4.9 +/- 0.3 g/day), nitrogen balance (95 +/- 7, 95 +/- 6 vs 139 +/- 7 mg/day) and nitrogen utilization (69 +/- 3, 67 +/- 3 vs 87 +/- 3%) compared with the control group. Administration of energy substrate in the SA and SB was a stronger denominator for O2 consumption and changes in RQ than the periods of physical activity. Control animals did not show any diurnal variations in O2 and RQ. Glucose, FFA and insulin were higher with CHO + FAT administration compared to AA infusion or simultaneous AA/CHO/FAT administration. In conclusion, the results suggest that simultaneous administration of a mixture of AA/CHO/FAT is preferable for whole body nitrogen economy during TPN.