Simultaneous treatment with IGF-I and GH additively increases anabolism in parenterally fed rats

We compared the effects of recombinant human insulin-like growth factor I [rhIGF-I, 800 micrograms/day, coinfused with total parenteral nutrition (TPN)], growth hormone (rhGH, 800 micrograms/day, subcutaneous injection twice daily), and simultaneous treatment with rhIGF-I and rhGH (800 + 800 micrograms/day) in rats subjected to surgical stress and maintained with TPN. Weight gain induced by IGF-I plus GH was double that shown by IGF-I or GH alone. Although weight gain was similar with IGF-I or GH, IGF-I selectively increased heart, kidney, thymus, spleen, and small intestine mass, whereas GH selectively increased gastrocnemius muscle mass. IGF-I and/or GH increased carcass protein and water while decreasing fat. Serum total and free IGF-I levels were highest with IGF-I plus GH. Serum rat GH levels were reduced with IGF-I and/or GH. IGF-I given with GH reversed the GH-induced increase in serum insulin. In summary, IGF-I and GH show tissue-specific anabolic effects, and simultaneous treatment with IGF-I plus GH additively increases anabolism during TPN.