Ricinoleic acid effects on rabbit intestine: an ultrastructural study.

In fasting rabbits, segments of ileum and colon were perfused with ricinoleic acid. This fatty acid is the active principle of castor oil and stimulates intestinal fluid secretion. Biopsies taken from perfused segments were examined by electron microscopy after staining with lanthanum hydroxide and ruthenium red. These stains, which typically bind to extracellular surfaces, were used to assess the integrity of junctional zones between cells. In this study, ricinoleate did not alter ruthenium or lanthanum staining in junctional areas, a finding suggesting that ricinoleate does not cause fluid secretion by selectively disrupting these areas.