Tight-Junction Complex

Figure 9 Magnification (X52,700) and schematic of tight junctional complex and lateral intercellular space. (From Ref. 74.)...

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... 

Gorodeski GI and Goldfarb J [1998] Seminal fluid factor increases the resistance of the tight junctional complex of the cultured human cervical epithelium CaSki. Fertil Steril 69 309-317... 

Abstract This chapter attempts to give an overview on the properties of the intestinal epithelium with regard to both, barriers to transcellular (transporter and efflux systems) and paracellular (tight junctional complex) drug absorption and transport systems and tight junction modulation. A short introduction into the relation between the innate immune system and modulation of paracellular permeability is equally given. 

Barriers to Paracellular Absorption 3.4.1 The Tight Junctional Complex... 

Tight junctional complexes zonula occludens ) in the retinal pigment epithelium prevent the ready movement of antibiotics and other drugs from the blood to the retina and vitreous. The retina is a developmental derivative of the neural tube wall and can be viewed as a direct extension of the brain it is not surprising that the blood-retinal barrier somewhat resembles the blood-brain barrier in form and function. Experimental evidence has shown that histamine does not alter the vascular permeability of the retina but does affect that of all other ocular tissues. The retina closely resembles the brain with respect to this trait. 

There are two cellular barriers that separate the brain extracellular fluid from the blood (see Figure 3.1). The first and largest interface is the brain capillary endothelial cells that form the BBB. The brain capillaries are a continuous layer of endothelial cells connected by well-developed tight junctional complexes.2 As a result of the tight junctions, passive diffusion of dmgs and solutes between the endothelial cells is restricted. In addition, brain capillary endothelial cells lack fenestrations (water-filled pores or channels within the plasma membrane) and have reduced pinocytic activity. These characteristics further restrict the movement of compounds from the blood into the extracellular environment of the brain.3-5... 

In vitro and in vivo experiments have shown that DON inhibits the intestinal absorption of nutrients including glucose and amino acids, by human and animal intestinal epithelial cells (lEC), and it also affects the permeability of the intestinal epithelium through modulation of the tight junction complexes. It must be noted that lEC are the first target of DON in cases of natural exposure through ingestion of contaminated food. 

Willis CL, Leach L, Clarke GJ et al (2004) Reversible disruption of tight junction complexes in the rat brain-blood barrier, following transitory focal astrocyte loss. GKa 48 1-13... 

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