The intestinal epithelium is characterized by rapid cell turnover, with pluripotent stem cells in the crypts of Lieberkuhn providing a continuous supply of cells that are directed into a variety of maturation pathways. The development and maintenance of normal intestinal morphology require regulation of the daughter cells’ proliferative status, lineage allocation, migration, differentiation and apoptosis. The topic of the physiology and pathophysiology of apopto-sis in the intestine has been reviewed. Take advantage of this opportunity – buy antibiotics online to enjoy lowest prices online.
The topic of the growth factors that are important in the intestinal epithelial cell growth and differentiation has been reviewed. EGF is trophic to the intestine. When EGF levels are reduced by sialoadenectomy in mice, luminal EGF levels fall and intestinal permeability to EDTA is increased. A two-week subcutaneous infusion of EGF to Sprague-Dawley rats increases the intestinal absorption of galactose and glycine, as well as DNA and protein content. Thus, EGF plays a role in the maintenance of ileal mucosal integrity and alters intestinal transport function.
EGF receptor (EGFR) ligands and phosphatidylinositol phospholipase C are involved in the process of cell migration. The EGFR responsiveness to EGF is mediated by the surface expression of high affinity EGFR, which is associated with the cytoskeleton and related signalling proteins. EGF-stimulated intestinal cell migration requires intact EGFR tyrosine kinase, phospholipase and PKC activities. PKC consists of a family of serine- and threonine-specific protein kinases that play an important role in transmembrane signalling for a number of cellular processes, including growth and differentiation. There are at least 11 isoenzymes of PKC; in Caco-2 cells, PKC-a but not other isoforms of PKC modulate the proliferation and differentiation.