Effects of Insulin-Like Growth Factor-1 and Growth Hormone on the Net Flux of Amino Acids across the Hind Limbs in the Surgically Traumatized Pig

Abstract

1. After surgery three groups of six female pigs weighing on average 52.2 kg (SD 3.5) received vehicle, recombinant insulin-like factor-1 (364.4 μg day−1 kg−1) or recombinant human growth hormone (467.7 m-i.u. day−1 kg−1) for two post-operative days. Vehicle and peptides were infused intravenously together with total parenteral nutrition providing 129 kJ day−1 kg−1 non-protein calories and 0.35 gN day−1 kg−1. 2. On both post-operative days the mean concentration of insulin-like growth factor-1 in arterial blood samples was clearly below presurgical levels in animals receiving vehicle or recombinant human growth hormone, whereas recombinant human insulin-like growth factor-1 infusions more than restored insulin-like growth factor-1 concentrations. These last samples, however, contained significantly (P<0.05) less insulin than those from other animals. 3. Infusion of recombinant human growth factor was often associated with higher circulating levels of amino acids compared with recombinant human insulin-like growth factor-1 infusions. Despite this, both hormones significantly (P < 0.05) increased the hind limb net balance of total amino acids on postoperative day 1. Net balances of −44.2, +69.5 and +100.9 μmol/min (pooled SE 35.3) were associated with infusion of vehicle, recombinant human insulinlike growth factor-1 and recombinant human growth hormone respectively. This response was also closely reflected in the group of non-essential amino acids. 4. The net efflux of alanine from the hind limbs was also significantly (P < 0.002) reduced, whereas glutamine was less affected. 5. On post-operative day 2, there was a general drop in cortisol and urea levels, implying a loss of catabolic tone. Concomitantly, most effects seen on amino acids flux after hormone administration on the previous day disappeared. 6. It is concluded that, in the acute catabolic state, both recombinant human insulin-like growth factor-1 and recombinant human growth hormone can prevent the erosion of body protein by increasing the peripheral net balance of amino acids and can thus increase the efficacy of total parenteral nutrition.