Magnitude of functional adaptation after intestinal resection

Intestinal adaptation after resection has been much studied, but rarely exa mined in an integrative context. Hence we assessed the effects of resection and subsequent adaptation on the quantitative relationship between dietary glucose load and gut capacity to transport glucose. The ratio of capacity to load is termed the "safety factor." Our objectives were to determine 1) the time course of intestinal adaptation after resection, 2) whether adapta tion is quantitatively complete, 3) whether survival requires maintaining a safety factor of at least 1.0 for glucose transport, 4) the effect of alte red energy demands on adaptation, and 5) the relationship between the amoun t of tissue removed and the magnitude of functional adaptation. We performe d 80% resection of the small intestine on Sprague-Dawley rats and measured small intestinal glucose uptake capacity, dietary glucose load, and gut gro ss morphology at 1, 5, and 10 wk postsurgery. Nearly all aspects of adaptat ion were complete by 1 wk postsurgery. After resection, remnant small intes tine mass increased by over fivefold within 1 wk, to reach 50-70% of its pr eresection value. However, mass-specific glucose uptake activity was reduce d, so that intestinal regeneration restored uptake capacity to only 33% of control values. Increased energetic demands had only modest effects on inte stinal adaptation. Although the safety factor for small intestinal glucose uptake remained <1.0 (i.e., capacity < load) after adaptation to resection, nearly all rats survived. Hindgut fermentation of nonabsorbed nutrients ap peared to contribute to that survival, despite inadequate small intestinal capacity. After less massive resection surgeries (25, 50, and 75% resection s), the percent increase in glucose uptake capacity increased with the amou nt of tissue removed.