An investigation of the penetration of ingested asbestos into the normal and abnormal intestinal mucosa of the rat.

To characterize the tissue response associated with the presence of asbestos fibres in the gastro-intestinal wall, duodenal tissues of Wistar rats were examined by light microscopy following injection of a suspension containing amosite fibres into the wall of the duodenum. Intestinal tissues were also examined by light microscopy following oral administration of amosite for 5 days to healthy animals and for up to 7 days to animals with induced gastro-intestinal ulcers. Injection of amosite into the wall of the gastro-intestinal tract resulted in granulomatous lesions characterized by large numbers of macrophages containing crystals with the polarizing characteristics of amosite fibres. Examination by polarizing light microscopy following ingestion of asbestos revealed no such lesions or other histopathological abnormalities in the gut wall of the healthy animals and no intracellular fibres were observed in the animals with ulcers. Light microscopy, therefore, yielded no pathological evidence of widespread transmigration of asbestos from the gastro-intestinal tract of rats, even under conditions of mucosal loss. Further studies involving analysis by electron microscopy are under way.