Basal lateral membrane

Despite the known renal disposition and nephrotoxicity of vancomycin, elucidation of its renal transport pathway remains incompletely defined. Early research by Sokol in rabbits demonstrated that vancomycin enters the proximal tubule cell across the basal lateral membrane via the organic acid transport system [186]. In addition, Sokol showed that vancomycin remains sequestered and concentrates inside the PTC. Vancomycin was found to enter the tubular lumen only by the much slower transport pathway of simple diffusion a secretory pathway was not found. This data would suggest that this renal transport pathway is a potential mechanism of vancomycin nephrotoxicity. However, there is not yet data that associates the PTC sequestration of vancomycin with nephrotoxicity or... 

Plausible as the above mechanism may seem, it may, however, not be the whole truth. An alternative mechanism is vesicular transport. In chicken intestine it has been shown that the only epithelial organelles that increased in Ca content as a result of calcitriol treatment were the lysosomes." The result lends support to a transport mechanism involving Ca + uptake across the brush-border membrane by endocytic vesicles, fusion of these vesicles with lysosomes, and possibly also delivery of Ca to the basal lateral membrane of the epithelial cell by exocytosis. This process would also explain the vitamin-D-induced alterations in brush-border-membrane lipid compositions as a consequences of preferential incorporation of certain types of lipids into the vesicles. Interestingly, the lysosomes in the chicken studies also contained high levels of calbin-... 

Besides investigations with whole tissue or isolated cells, studies with vesicles isolated from luminal or basal-lateral membranes of small intestine or kidney gave... 

Lasb, L.H. Jones, D.P. Uptake of tbe glutathione conjugate S-(l,2-dichlorovinyljglutathione by renal basal-lateral membrane vesicles and isolated kidney cells. Mol. Pharmacol. 1985, 28, 278-282. 

Lash, L.H. Jones, D.P. Renal glutathione transport characteristics of the sodium-dependent system in the basal-lateral membrane. J. Biol. Chem. 1984, 259, 14508-14514. 

Nemere, 1., Dormanen, M.C., Hammond, M.W., Okamura, W.H. Norman, A.W. (1994). Identification of a specific binding protein for 1 25 dihydroxyvitamin Dj in basal-lateral membranes of chick intestinal epithelium and the relationship to transcalthachia. ]. Biol Chem., 269, 23750-6. 

Larsson, D., Nemere, L, Sundell, K. 2001. Putative basal lateral membrane receptors for 24,25-dihydroxyvitamin D(3) in carp and Atlantic cod enterocytes Characterization of binding and effects on intracellular calcium regulation. J. Cell Biochem. 83(2) 171-86. 

The cytoskeleton is involved in the maintenance of cell shape and cytoplasmic processes (e.g., microvilli). In polarized epithelial cells, distinct cyto-cortical cytoskeletal complexes are associated with the apical and basal-lateral domains of the plasma membrane (Rodriguez-Boulan and Nelson, 1989 Mays et al., 1994). 

Their cytoplasmic membrane is bristled up with microvillosities and micropilis. They increase the exchange surface with the lacrymal secretion and enable its fixing. Their lateral and basal cytoplasmic membranes have got junctional complexes uniting these superficial cells together. There are three types of junctional complexes ... 

Electron micrographs of these glands show structures which would be in keeping with this interpretation614. Arising from the basal lamina are numerous membranous infoldings. The lateral membranes are closed by tight junctions at the lumenal surface but freely open into to blood sinuses on the serosal surface. The lumenal surface contains many microvilli (Fig. 6). 

The lateral cell membrane has a barrier function similar to that of the basal cell membrane. After passing this membrane, drug molecules enter the subcellular space. 

The apical membrane of a polarised cell is that part of the plasma membrane that forms its luminal surface, particularly so in the case of epithelial and endothehal cells. The basolateral membrane of a polarised cell refers to that part of the plasma membrane that forms its basal and lateral surfaces. Proteins are free to move from the basal to lateral surfaces, but not to the apical surface tight junctions, which join epithehal cells near their apical surfaces, prevent migration of proteins to the apical surface. The apical surface is therefore distinct from the basal/lateral surfaces. 

The apical side of the cell faces the lumen this side is also the mucosal side in many tissues, The basal side faces the interstitial fluid and the capillaries this side is also called the serosal side. The sides of the cell facing adjacent cells are called the lateral sides. Nutrients entering and exiting the basal and lateral membranes (basolateral membrane) can freely enter and exit the permeable membranes of nearby capillaries. Thus, the Na secreted by the basolateral membrane can enter the circulatory system. Potassium leaking from the capillaries can be taken up by the Na,K-ATPase of the basolateral membrane. The cells are connected to each other by impermeable junctions called tight junctions. 

The basal lateral plasma membrane contains at least two types of Ca + pumps that also may play a role in Ca " " uptake, one ATP-driven, one driven by a concurrent flow of Na" " ions into the cytoplasm (i.e., a Na -Ca + antiport see Figure 3.8). We discuss these types of transporting proteins in the next subsection. 

The trapping and transport of iodide occurs at the basal cell membrane. It is an active ATP-dependent process and is probably facilitated by the iodine-binding property of phospholipid. The later stages of biosyn-... 

In order to reduce such interferences, successful efforts have been made to isolate the cell membranes, or even their transport-active constituents. One way to achieve this is by preparation of isolated membranes which have a natural tendency to form closed and homogenous vesicles [31,32]. Another approach is by reconstituted systems , i.e. to isolate membrane components involved in specific transport processes, and to incorporate them in artificial lipid membranes, usually liposomes [33,34]. Vesicles have been successfully prepared from various cells and tissues and tested for transport activities. Whenever membranous material has been isolated from other cellular components it tends to form vesicles spontaneously, sometimes with an uniform orientation, right-side-out or inside-out vesicles, respectively. For mixtures of vesicles of the two orientations, methods were developed to separate the two polarities. Furthermore, one can separate vesicles from different cell types or even from different regions of the cell, e.g. brush-border membranes form basal lateral ones [35,36]. 

Consider the lateral intercellular space, or channel (Fig. 6) as a compartment bounded by apical (A), basal (B), and lateral (L) membranes. In this model, the apical membrane corresponds to the tight junction, the basal membrane to the combined basement membrane plus subepithelial tissue, and the lateral membrane... 

Basolateral membrane, characteristic especially for epithelial cells, whose basal and lateral membranes remain identical both in activity and in composition. 

Kinne, R., Murer, H., Kinne-Saffran, E., Thees, M., and Sachs, G., 1975, Sugar transport by renal plasma membrane vesicles Characterization of the systems in the brush-border microvilli and basal-lateral plasma membranes, /. Membrane Biol. 21 375. 

Liang, C. T., and Sacktor, B., 1977, Preparation of renal cortex basal-lateral and brush border membranes. Localization of adenylate cyclase and guanylate cyclase activities, Biochim. Biophys. Acta 466 474. 

Figure 2 Comparison of intestinal epithelial cells in culture and in situ. (A) Human colon Caco-2 cells grown in culture for 16 days on a semiporous filter. (B) Epithelial layer of rat jejunum. AP, apical or luminal membrane B, basal or abluminal membrane BM, basement membrane G, goblet cell LS, lateral space mv, microvilli Nu, nucleus TJ, tight junction. Bars equal 10 pm. 

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