Resection upregulates the IGF-I system of parenterally fed rats with jejunocolic anastomosis

Rats maintained with parenteral nutrition following 60% jejunoileal resecti on plus cecectomy exhibit minimal adaptive growth in the residual jejunum b ut a dramatic adaptive growth in the residual colon. Coinfusion of insulin- like growth factor I (IGF-I) with parenteral nutrition induces jejunal grow th but has minimal effects in the colon. Our objective was to study the rol e of the endogenous IGF-I system in the differential responses of jejunum a nd colon to resection and/or IGF-I during parenteral nutrition. We measured concentrations of immunoreactive IGF-I in plasma, jejunum, and colon, IGF- I receptor binding, and levels of IGF receptor, IGF-I, IGF binding protein (IGFBP)-3 and IGFBP-5 mRNA in residual jejunum and colon 7 days after resec tion and/or IGF-I treatment. IGF-I receptor number was increased (74-99%) i n jejunum and colon due to resection; IGF-I mRNA was increased 5-fold in je junum and 15-fold in colon due to resection. Resection increased circulatin g IGFBPs but did not alter plasma IGF-I concentration. Resection induced co lonic growth in association with significantly greater colonic IGFBP-5 mRNA and significantly lower colonic immunoreactive IGF-I. IGF-I treatment had no significant effect on IGF-I mRNA or IGF-I receptor number. Concentration s of plasma and jejunal immunoreactive IGF-I were significantly increased i n rats given IGF-I in association with jejunal growth. IGF-I treatment sign ificantly increased IGFBP-5 mRNA in the jejunum, which also correlated with jejunal growth. Thus resection upregulated IGF-I receptor number and IGF-I mRNA in residual jejunum and colon, but differential adaptation of these s egments correlated with differential regulation of IGFBP-5 mRNA.