Lysosomes of the liver and the duodenal enterocytes, a site of handling of two rare earths. Ultrastructural and microanalytical study.

The frequent use of some trace elements such as gadolinium and terbium in medicine and modern industries make us worry about their behavior in the organism. In this work, we study the intracellular localization in the liver and in the intestinal mucosa of two rare earths, gadolinium and terbium, after intraperitoneal and intragastric administration. Three methods of observation and microanalysis were used: conventional transmission electron microscopy, secondary ion mass spectrometry, and electron probe microanalysis. After intraperitoneal administration, gadolinium and terbium were detected with phosphorus in lysosomes of hepatocytes and Küppfer cells and in territories near to biliary canalicule. One hour after intragastric administration, gadolinium and terbium were concentrated in lysosomes of the apical part of duodenal enterocytes. No gadolinium or terbium was detected in duodenum 4 days after administration. After intragastric administration, the microanalytical techniques failed to detect gadolinium or terbium in liver whatever the time of sampling. This mechanism of concentration-precipitation in the lysosomes of enterocytes limits the diffusion through the digestive barrier of foreign elements and then permits their elimination with apoptotic cells in the intestinal lumen. Some of these elements may be toxic, and none of them have a recognized physiological function. The intestinal mucosa plays an important role in the protection of the organism against the invasion of foreign elements.