Epithelial cells amino acids

An individual has been shown to have a deficiency in an intestinal epithelial cell amino acid transport system for leucine. However,... 

Thyrotropin (TSH) regulates the production and secretion of thyroid hormones as well as thyroid epithelial cell growth via the TSH receptor. The TSH receptor belongs to the family of G protein-coupled receptors. It is composed of 764 amino acids. The receptor contains a long hydrophilic region orientated towards the exterior of the cell (ectodomain), 7 hydrophobic transmembrane domains and a short cytoplasmic region. 

Biochemical studies of plasma membrane Na /H exchangers have been directed at two major goals (1) identification of amino acids that are involved in the transport mechanism and (2) identification and characterization of the transport pro-tein(s). To date, most studies have been performed on the amiloride-resistant form of Na /H" exchanger that is present in apical or brush border membrane vesicles from mammalian kidney, probably because of the relative abundance of transport activity in this starting material. However, some studies have also been performed on the amiloride-sensitive isoform present in non-epithelial cells. 

Active reabsorption occurs when the movement of a given substance across the luminal surface or the basolateral surface of the tubular epithelial cell requires energy. Substances that are actively reabsorbed from the tubule include glucose amino acids and Na+, POy3, and Ca++ ions. Three generalizations can be made regarding the tubular reabsorption of sodium, chloride, and water ... 

Hu, M. and R. Borchardt. Transport of a large neutral amino acid in a human intestinal epithelial cell line (Caco-2) uptake and efflux of phenylalanine., Biochim. Biophys. Acta 1992, 3335, 233-244... 

Some of the zinc taken up by the intestinal epithelial cells is rapidly transferred to the portal plasma where it associates with albumin, a2 macroglobulin, and amino acids. About 67% of the zinc in plasma is bound to albumin, and about 3% is stored in liver (Stemlieb 1988). Soluble organozinc complexes are passively absorbed across the plasma membrane of the mucosa of the intestinal villi the soluble, nondiffusable complexes are transported in the intestinal products and excreted in feces (NAS 1979). Zinc loss from urine and sweat is usually small (Casey and Hambidge... 

The movement of solutes from the external environment into the cell is usually achieved using cell membrane-spanning proteins that facilitate solute transfer. These are necessary, since most solutes (e.g. sugars, amino acids, salts) will not readily diffuse through the hydrophobic cell membrane. Movement of solutes into the epithelial cell can involve a variety of protein carriers or channels including (see Figure 1) ... 

Rabito, C.A. and Karish, M.V (1982). Polarized amino acid transport by an epithelial cell line of renal origin (LLC-PKj). The hasolateral systems. J. Biol. Chem. 257 6802-6808. 

---