Rabbit ileal mucosa exposed to fatty acids, bile acids, and other secretagogues. Scanning electron microscopic appearances.

Segments of rabbit ileum were examined by scanning electron microscopy (SEM) after exposure to various compounds known to stimulate fluid secretion in the small intestine. After perfusion with ricinoleate (castor oil) at a 10 mM concentration, striking changes were observed at villus tips and on the apicolateral surfaces of villi; erosions at tips were confirmed by light microscopy of the same pieces of tissue examined by SEM. The appearances after ricinoleate were reversed in part during perfusion with control buffer for 2 hr. Statistical comparisons between control perfused, treated, and reversal tissues showed that the "damage" produced by ricinoleate, and its reversal, was significant statistically. Tissues treated with other intestinal secretagogues, oleic acid (10 mM), deoxycholic acid (4 mM), cholic acid (4 mM), dioctyl sodium sulfosuccinate (6 mM), and cholera toxin (1 microgram/ml) also showed surface changes by SEM. Fluid secretion, produced by an osmotic agent (mannitol) was not associated with "damage." Changes in structure of the mucosal surface after exposure to intestinal secretagogues should be considered as one possible mechanism of impaired fluid transport.