Epithelial tissue cell membrane

In respiratory epithelial (RE) cells the Cl -conductance was attributed to the ICOR channel. In fact, it was reported by Frizzell et al. and Welsh s laboratories that catecholamines increased the incidence of ICOR channels in cell attached patches of normal RE cells but failed to do so in CF cells [110,111], Later both laboratories presented data on excised membrane patches of RE cells in which the protein kinase A which was added to the cytosolic side produced ICOR channel activity in the normal cells but not in the CF tissues [19,20]. This finding was reproduced by Guggino and coworkers [22] for RE cells and by others for lymphocytes [46]. Protein kinase C at physiological Ca -activities had a comparable effect in normal cells but also failed to function in CF cells [22,112]. 

Symporters are membrane-spanning proteins which translocate two or more solutes in the same direction across the cell membrane. In epithelial tissue, such... 

Serosal membrane The cell membrane of the epithelial cell adjacent to the blood (serosal) side of the tissue. Sometimes also called the basolateral membrane in some gill and intestinal epithelia, because anatomical folds of the serosal membrane may extend laterally along the sides of the epithelial cells. 

Polar Cell Systems for Membrane Transport Studies Direct current electrical measurement in epithelia steady-state and transient analysis, 171, 607 impedance analysis in tight epithelia, 171, 628 electrical impedance analysis of leaky epithelia theory, techniques, and leak artifact problems, 171, 642 patch-clamp experiments in epithelia activation by hormones or neurotransmitters, 171, 663 ionic permeation mechanisms in epithelia biionic potentials, dilution potentials, conductances, and streaming potentials, 171, 678 use of ionophores in epithelia characterizing membrane properties, 171, 715 cultures as epithelial models porous-bottom culture dishes for studying transport and differentiation, 171, 736 volume regulation in epithelia experimental approaches, 171, 744 scanning electrode localization of transport pathways in epithelial tissues, 171, 792. 

It is well established today that drug absorption through the alimentary canal walls is a complex event, which involves, in many cases, parallel or sequent microprocesses at the apical membrane of the absorptive cell (enterocyte) or between them (paracellular absorption). In addition to the various types of diffusion processes across the enterocyte membrane, numerous specific proteins—transporters and efflux pumps—are involved in the intricate drug absorption process. In the following sections the various epithelial tissues of the different organs of the GI tract will be looked at briefly. A review of major drug absorption mechanisms across epithelial cells, as they are customary today will follow. 

Membranous epithelial M cells are a part of the organized mucosa-associated lymphoid tissue (O-MALT). These cells are specialized for antigen sampling. Also, they are exploited as a route of invasion by several pathogens.39 M cells are concentrated in follicle-associated epithelial (FAE) tissue called Peyer s patches in the small intestine. As M cells carry out endocytotic transport, they can be potential vehicles for mucosal drug and vaccine delivery. 

The eyes, mouth, nose, vagina and rectum have mucous membranes. These are sheets of epithelial (lining) cells that are moist owing to the production of a slimy secretion called mucus. Additionally, they line the alimentary (digestive) tract, respiratory tract and genito-urinary tracts. The mucus has a protective role to prevent injury to underlying tissues and traps foreign particles in the respiratory system. 

Desmosomes are intercellular junctions, consisting of two cell membranes, separated by an interspace. The interspace contains dense fibrillar plaques rich in cell adhesion proteins of the cadherin type. Desmosomes are important for cell-cell adhesion and communication. Epithelial tissue in the body stretched mechanically is rich on desmosomes. 

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