Light and electron-microscopic changes in the colon of the guinea pig after treatment with anthranoid and non-anthranoid laxatives.

Male guinea pigs were treated with senna pods, sennosides, danthron or bisacodyl by gastric intubation for 14 consecutive days. The animals were then killed and the intestine was evaluated by light and electron-microscopic techniques. Macroscopically, the mucosa of the cecum and upper colon was brown in color in the animals receiving anthranoid laxatives. No visible changes were detectable in the bisacodyl group. Evaluation by light and electron microscopy revealed cytoplasmic degeneration and increased apoptosis in the colonic surface epithelium after all laxatives. Most of the resulting apoptotic bodies were found in the lamina propria or had been phagocytosed by stromal macrophages, where they had been transformed into dark brown (anthranoids) or grey to light brown (bisacodyl) pigments. The intestinal changes were most pronounced in the cecum and decreased towards the distal part of the colon. It can be concluded that the morphological changes in the large intestine were similar in anthranoid and non-anthranoid treatment, with the exception that the pigments found in macrophages differed in color and were therefore not always detectable macroscopically.