Regulation of Paracellular Permeability

In the past, changes in RTj were viewed in terms of assembly/disassembly of the tight junctional complex (reviewed in 93). Recent studies in human vaginal-cervical epithelia have shown acute and reversible modulation of Rtj that are the result of conformational changes in assembled tight junctions [13], The examples presented below relate to effects of modulation of extracellular calcium level (Ca0) and treatments with ATR 

These data on Ca0 effects observed in the low-resistance epithelia raised a question related to their physiological relevance, in light of the tight regulation of extracellular Ca2+ level at 1.2-1.5 mM range. The extracellular Ca2+ level at the cell surface is likely to vary because of the presence of cell surface or cell secreted Ca2+-binding proteins [106, 107]. Therefore, the experimental EC50 

In human vaginal-cervical epithelia, occludin appears to play a significant role in the regulation of 7 tj- In the vaginal-cervical epithelia, occludin is present in two forms the full length 65-kDa isoform and a truncated 50-kDa isoform [35,43], A shift from 65 kDa to 50 kDa dominance is associated with abrogation of [35,43], suggesting that in low-resistance epithelia, occludin plays an important role in 7 tj- 

---

Gorodeski GI, Hopfer U, De Santis BJ, Eckert RL, Rorke ER, and Utian WH [1995] Biphasic regulation of paracellular permeability in human cervical cells by two distinct nucleotide receptors. Am J Physiol 268 C1215-C1226... 

Gorodeski GI [2001] Estrogen biphasic regulation of paracellular permeability of cultured human vaginal-cervical epithelia. J Clin Endocrinol Metab 86 4233-4243... 

Baida MS, Flores-Maldonado C, Cereijido M, and Matter K [2000] Multiple domains of occludin are involved in the regulation of paracellular permeability. J Cell Biochem 78 85-96... 

Careful observation at the borders of the enterocytes reveals a close juxtaposition of the membranes of adjacent epithelial cells, identified as zonulae occludens, located at the apical neck of the epithelial cells [168], The zonulae occludens is composed of apical complex the tight junctions and more basal structure underneath, the adherens junctions (also referred to as intermediate junctions) [169,170]. The adherens junctions are linked to the actomyosin ring at the cell circumference. This actin cytoskeleton, which forms a perijunctional area at the apical neck of the epithelial cells, is the cause for their polarized nature (Figure 1.12). The classical functions of tight junctions are the regulation of paracellular permeability and the restriction of apical basolateral intramembrane diffusion of lipids (cell polarity housekeeping). 

Turner, J.R. 2000. Show me the pathway Regulation of paracellular permeability by Na+-glucose cotransport. Adv Drug Deliv Rev 41 265. 

The adherent junctions are ubiquitously found in the cerebral vasculature and mediate several functions, including the adhesion of endothelial cells to each other, contact inhibition during remodeling, and growth of the vasculature, and mediate in part the regulation of paracellular permeability (Hawkins and Davis, 2005). The most important components of the adherent junctions are vascular endothelial... 

Anderson, J.M. van Itallie, C.M. Tight junctions and the molecular basis for regulation of paracellular permeability. Am. J. Physiol. 1995, 269 (32), G467-G475. 

---