INTESTINAL DIMENSIONS OF MICE DIVERGENTLY SELECTED FOR BODY-WEIGHT

Background: Selection for body weight provides important animal models for studying mechanisms of growth regulation, This study evaluated gr owth responses of the gastrointestinal tract (GIT) to long-term select ion of mice for high (H line) or low (L line) 8-week body weight as co mpared with random-bred controls (C line), Methods: Weights and dimens ions of the various parts of the GIT were recorded from 8-month-old mi ce, For light microscopic stereological analyses, samples were taken f rom eight equidistant locations covering the whole jejunum/ileum. Vert ical sections were used for estimation of fractional volumes of mucosa , submucosa, and muscularis and of villous surface area density and fo r measurement of villus length, Results: Differences between groups in weights and dimensions of the various parts of the GIT were more pron ounced in the proximal than in the distal segments, with greatest valu es in H, followed by C and L mice, Relative to body weight, intestinal growth was similar in the three lines, except for significantly (P < 0.001) increased relative weights of jejunum/ileum, caecum, and colon in L mice, The fractional volume of mucosa and villus length decreased , whereas the fractional volumes of submucosa and muscularis increased from the proximal to the distal locations, The absolute volume of muc osa was greatest in H mice, followed by C and L mice, Relative to body weight, the volume of mucosa was significantly (P < 0.01) greater in L mice than in the two other lines, The mean total villous surface are a of jejunum/ileum was significantly (P < 0.01) different among the th ree lines (L line: 144 cm(2) C line: 227 cm(2): H line: 304 cm(2)) but proportionate to differences in metabolic body weight, Conclusions: S election for body weight affected various parts of the GIT to a differ ent extent, The parameters investigated changed markedly along the sma ll intestine, demonstrating the need for systematic sampling, Vertical section stereology provides unbiased estimates of total villous surfa ce area, which is a parameter of major biological significance. (C) 19 98 Wiley-Liss, Inc.