Toxic effect on the rat small intestine of chronic administration of asbestos in drinking water.

Sprague-Dawley rats were given a 0.5 g/l Chrysotile asbestos solution in their drinking water (approximately 7 mg/day ingested) for 1.5 years and compared to control rats of the same age. During this time there were no differences in weight or appearance of the asbestos-treated rats in comparison to controls maintained under the same conditions. However, when in vivo intestinal permeability studies were performed using a gavage/urinary collection technique, some significant changes were noted. The recovery of lactulose in the urine of asbestos-treated rats was 0.66 +/- 0.07%, significantly less than that of the controls (1.01 +/- 0.08, P less than 0.005). The recovery of mannitol was similarly decreased (2.2 +/- 0.28 vs. 3.0 +/- 0.17, P less than 0.02), but that of rhamnose was unchanged. Creatinine clearance studies indicated that there was no impairment of kidney function in the asbestos-treated group and polarized light microscopy did not reveal any asbestos fibers in sections of the small bowel. The results suggest that the chronic exposure of rats to asbestos fibers in the drinking water results in a decreased ability of the intestine to absorb some non-metabolizable sugars.