LENTEN CELL - ULTRASTRUCTURE, ABSORPTIVE PROPERTIES, AND ENZYME EXPRESSION OF A NOVEL TYPE OF CELL IN THE NEWBORN AND SUCKLING PIG INTESTINAL EPITHELIUM

Background: The small intestinal epithelium is made up of columnar abs orptive enterocytes and a smaller number of specialized nonabsorptive cells, including goblet cells, enteroendocrine cells, M cells, cup cel ls, and tuft cells. During a study on milk protein absorption in newbo rn pigs, we identified an enterocyte that showed no uptake of milk pro teins and that could be found only in the jejunum and ileum of pigs du ring the first 2 weeks of life. We call this previously undescribed en terocyte the lenten cell. Methods: We used light microscopy and transm ission electron microscopy in conjunction with immunolabelling and cyt ochemical techniques to determine the occurrence, ultrastructure, abso rptive properties, and brush border hydrolase expression of lenten cel ls. Results: Lenten cells constituted similar to 1-2% of the villous e pithelium. They were seen in newborn and suckling pigs 1-9 days of age , but were not found in weaned pigs. Morphologically, lenten cells wer e spindle- or wineglass-shaped, with a ventrally sited nucleus and an electron-dense cytoplasm with numerous cytokeratin filaments. Lenten c ells had a normal brush border with microvilli that were slightly thic ker than those of absorptive enterocytes, but they did not express the brush border hydrolases lactase, aminopeptidase N, and alkaline phosp hatase. Lenten cells did not endocytose milk proteins or horseradish p eroxidase, but contained some endocytic or secretory vacuoles and a fe w dense granules. Conclusions: No role for lenten cells has been ident ified in this study, but presence of these cells during the neonatal p eriod, when growth and differentiation of the gastrointestinal tract i s at a peak, clearly suggests that lenten cells may play a role in thi s process. (C) 1996 Wiley-Liss, Inc.