INSULIN-LIKE GROWTH-FACTOR-I (IGF-I) RESPONSES IN RATS MAINTAINED WITH INTRAVENOUS OR INTRAGASTRIC INFUSION OF TOTAL PARENTERAL-NUTRITION SOLUTIONS CONTAINING MEDIUM-CHAIN OR LONG-CHAIN TRIGLYCERIDE EMULSIONS

Our objective was to determine how intravenous or intragastric feeding affects serum concentrations of insulin-like growth factor (IGF)-I an d- II and IGF binding proteins (IGFBP), and hepatic abundance of IGF-I mRNA. Male Fischer 344 rats (235-246 g) were fed for 14 d by intraven ous or intragastric infusion with total parenteral nutrition (TPN) sol utions providing 65% of energy from long-chain triglyceride (LCT) or a 3:1 admixture of medium-chain triglyceride (MCT) and LCT emulsions (M CT/LCT). Twice as much TPN solution was required per gram of weight ga in with MCT/LCT compared with LCT infusion (P < 0.0003). Serum IGF-I a nd -II concentrations and hepatic IGF-I mRNA abundance were net signif icantly different. Circulating concentrations of IGFBPs with molecular weights of 38 000-43 000 (IGFBP-3) were significantly greater with in travenous MCT/LCT than with intravenous LCT infusion. Our data demonst rate that reduced growth in rats given TPN containing MCT/LCT compared with LCT emulsions is not associated with reduced serum IGF-I concent rations or hepatic abundance of IGF-I mRNA, although serum IGFBPs are elevated.