An Ultrastructural Study on the Small Intestinal Absorptive Cells of Rat after Administration of Lead Acetate

Kim, Dong Sug; Kim, Kee Kwon; Chang, Eun Sook

Abstract

This study was carried out to visualize lead by Timm sulphide silver method and to define lead-induced change of duodenal absorptive cells of rat after administration of 0.01% lead acetate with drinking water. Sprague-Dawley rats, weighing 250g, were used, and they were orally administered with 0.01% sodium acetate and sacrificed at 0.5, 1, 1.5 hours and 2, 7, 15, 30, 45, 60 days after administration. A portion of duodenal tissue was observed under light microscope, scanning and transmission electron microscopes after development with Danscher method. The blood lead concentration in experimental group began to increase from the 2nd day after administration, and it increased gradually until the 45th day and decreased at the 60th day. On light microscope, many brown lead granules were observed at the villi tip at the 2nd day. There is mild blunting of villi tip at the 45th day. At the 60th day, most of the villi were mildly shortened and showed lymphangiectasia. On scanning electron microscope, the villi tip was mildly blunted and the extrusion zone became irregular at the 45th day. The depth of creases did not change. At the 60th day, the villi tip was moderately blunted and the extrusion zone was markedly irregular. The depth of creases increased. On transmission electron microscope, at 0.5 hour after oral administration, numerous lead granules were diffusely scattered and were not confined to any specific microorganelles. The lead granules decreased with time. At the 7th 15th day, the intercellular spaces were widened and several vacuoles appeared and the condensation of mitochondrial matrix. There was also ribosomal detachment from RER, and there was neither secondary lysosomes or post-lysosomes. At the 30th and 45th day, secondary lysosomes appeared and the condensation of mitochondrial matrix with early formation of myelin figures was noted. At the 60th day, the intercellular space widening extended to the upper most portion of the cells, and nonspeciqic degenerative changes became severe. In view of above mentioned findings, it can be concluded that passive diffusion as well as active transport was partly involved in the absorption of lead. Most of the changes of microorganelle are compatible with nonspecific degenerative changes which could occur due to impairment of oxidative phosphorylation.