Effects of growth hormone on intestinal morphology of genetically dwarf rats

Three groups of Lewis rat were studied: dwarf rats, genetically deficient in growth hormone; rehabilitated dwarf rats treated with exogenous growth hormone (GH); and normal wild-type rats. The small intestine of each animal was removed and simple random transverse sections were taken from the proximal and distal regions. The profile areas of villi, crypt and muscle were estimated by point count analysis and combined with intestinal length measurements to obtain absolute volumes. Villus and primary mucosal surface areas were estimated from intersection counts and linear measurements were made of epithelial cell height. Distally, villous volume and surface area were reduced by 42% and 39%, respectively, in the dwarfs compared with controls. These features were significantly smaller (P < 0.01) in dwarfs distally than proximally. Crypt volume and epithelial cell height were decreased equally in both proximal and distal regions of the intestine of dwarf rats. Following GH administration both features increased, crypt volume overshooting control values. These results indicate that GH deficiency has a subtle effect on intestinal morphology and that the intestine is more sensitive distally than proximally. Reconstitution with GH is capable of reversing many of these changes.