Differential effect of growth factors on intestinal wall components

Both the mucosal and muscle layers respond to surgical manipulation of the small intestine. Various growth factors influence the mucosal response but less is known about changes in the muscle layers. Our aim was to evaluate the effect of epidermal growth factor (EGF) and octreotide (OCT) on changes in the intestinal wall induced by serosal patching. Twenty-four New Zealand white rabbits (3-4 kg) were studied. Group I (n=6) were unoperated controls. Group II (n=6) underwent creation of a 2 X 5-cm serosal patch in the ileum. Group III (n=6) and Group IV (n=6) received EGF (1.5 micrometer/kg/hr SQ) or OCT (1000 microgram/d SQ) after serosal patching. Wall composition, collagen content, and mucosal proliferation and enzyme activity of normal adjacent ileum were studied after 7 days. Serosal patching resulted in thickening of the mucosa and muscle layers (circular muscle: 189 +/- 54 vs 86 +/- 33 microns longitudinal muscle: 105 +/- 17 vs 55 +/- 12 microns P < 0.05) with increased proliferation and collagen content. EGF augmented the mucosal thickening (705 +/- 66 vs 573 +/- 94 microns, P < 0.05) and stimulated mucosal proliferation but inhibited the changes in muscle and collagen content. OCT inhibited the mucosal thickening and proliferation, but had less affect on the muscle. Disaccharidase activity was similar in all of the patched groups. We conclude the following. (1) Growth factors have differential effects on the intestinal wall components. (2) EGF stimulates the mucosa but has inhibitory effects on induced muscle changes. (3) Octreotide inhibits mucosal proliferation with less effect on muscle. (4) These observations have important implications for the therapeutic applications of these agents.