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Absorption of horseradish peroxidase by the small intestinal epithelium in postnatal developing rats
Insights
Developing rat intestines show changes in how they absorb substances. After weaning, the small intestine
Area of Science:
- Gastroenterology
- Cell Biology
- Developmental Biology
Background:
- The small intestine's epithelial cells undergo significant functional and structural changes during development.
- Understanding the absorption mechanisms in neonatal versus adult rats is crucial for developmental biology.
Purpose of the Study:
- To investigate the developmental changes in the absorption and localization of exogenous peroxidase in the small intestine of rats.
- To compare peroxidase uptake in neonatal, weaning, and adult rats.
Main Methods:
- Intraluminal injection of horseradish peroxidase into the small intestine of rats.
- Electron microscopy was used to study the localization of peroxidase in duodenal, jejunal, and ileal epithelial cells.
Main Results:
- In neonatal rats (up to 14 days), absorbed peroxidase was abundant in the microvillous membrane, apical tubulo-vacuolar system, Golgi apparatus, lateral and basal membranes, and capillary endothelial cells.
- At weaning, the tubulo-vacuolar system disappeared from duodenal and jejunal cells, with peroxidase localization similar to adults (microvilli, lateral/basal membranes, Golgi, cytoplasmic vesicles/vacuoles).
- In ileal cells, peroxidase was found in the tubulo-vacuolar system and supranuclear vacuole during suckling but was absent after weaning when these structures were lost.
Conclusions:
- The small intestine's absorptive mechanisms, particularly the role of the tubulo-vacuolar system and supranuclear vacuole, mature significantly around the weaning period.
- These developmental changes in cellular structures impact the pathway and extent of exogenous substance absorption in the rat ileum.
Abstract:
After an intraluminal injection of horseradish peroxidase into the small intestine, the localization of peroxidase was studied in neonatal developing and adult rats by means of electron microscopy. Until around the 14th day of the neonatal period absorbed peroxidase granules in the duodenal and jejunal epithelium were abundant in the microvillous membrane, the apical tubulo-vacuolar system, and the Golgi apparatus, and on the lateral cell and basal membranes, and the luminal surfaces of the capillary cells. At the weaning period the tubulo-vacuolar system was absent in the duodenal and jejunal epithelial cells, and at that point absorbed peroxidase was observed in the same sites as in the adult rats: the microvillous membrane, the lateral cell and basal membranes, the Golgi apparatus, and the vesicles and vacuoles of the cytoplasm. During the suckling period, in the ileal epithelial cells exogenous peroxidase was found on the microvilli, in the tubulo-vacuolar system, in the supranuclear vacuole, in the Golgi apparatus, on the lateral cell and basal membranes, and also on the luminal surface of the endothelial cells of blood capillaries. When the tubulo-vacuolar system and the supranuclear vacuole were lost from the ileal cells at the weaning period, no exogenous peroxidase uptake was observed in the absorptive cell of the ileal epithelium.