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The small intestinal epithelium is made up of columnar absorptive enterocytes and a smaller number of specialized non-absorptive cells, including goblet cells, enteroendocrine cells, M cells, cup cells, and tuft cells. During a study on milk protein absorption in newborn pigs, we identified an enterocyte that showed no uptake of milk proteins and that could be found only in the jejunum and ileum of pigs during the first 2 weeks of life. We call this previously undescribed enterocyte the lenten cell.We used light microscopy and transmission electron microscopy in conjunction with immunolabelling and cytochemical techniques to determine the occurrence, ultrastructure, absorptive properties, and brush border hydrolase expression of lenten cells.Lenten cells constituted approximately 1-2% of the villous epithelium. They were seen in newborn and suckling pigs 1-9 days of age, but were not found in weaned pigs. Morphologically, lenten cells were spindle- or wineglass-shaped, with a ventrally sited nucleus and an electron-dense cytoplasm with numerous cytokeratin filaments. Lenten cells had a normal brush border with microvilli that were slightly thicker than those of absorptive enterocytes, but they did not express the brush border hydrolases lactase, aminopeptidase N, and alkaline phosphatase. Lenten cells did not endocytose milk proteins or horseradish peroxidase, but contained some endocytic or secretory vacuoles and a few dense granules.No role for lenten cells has been identified in this study, but presence of these cells during the neonatal period, when growth and differentiation of the gastrointestinal tract is at a peak, clearly suggests that lenten cells may play a role in this process. |
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