Transepithelial electrical measurements

The bond graph method of network thermodynamics is widely used in studying homogeneous and heterogeneous membrane transport. Electroosmosis and volume changes within the compartments are the critical properties in the mechanism of cell membrane transport, and these properties can be predicted by the bond graph method of network thermodynamics. In another study, a network thermodynamics model was developed to describe the role of epithelial ion transport. The model has four membranes with series and parallel pathways and three transported ions, and simulates the system at both steady-state and transient transepithelial electrical measurements. 

Ii H, Sheppard DN, Hug MJ (2004) Transepithelial electrical measurements with the Ussing chamber. J Cyst Fibres 3 Suppl 2 123-126... 

Cell cultures. MDCK cells were seeded in the Transwells at a density of 2.2 x 104 cells/cm. Cells were fed by changing medium in both upper (apical) and lower (basal) compartments periodically. Confluent monolayers were obtained at 5-7 days post-inoculation, when the cell density reached 4.5-5.0 x 105 cells/cm2, and a transepithelial electrical resistance (TEER) of about 2,000 ohms cm2 was measured using an epithelial voltohmmeter (EVOM, World Precision Instruments, West Haven, CT). The amount of FBS in the cell culture medium could be decreased as the cells approached their maximum resistance, and could be maintained at that point for 2 days or longer in medium containing 1% FBS. 

The in vitro system we have been using to study the transepithelial transport is cultured Madin-Darby canine kidney (MDCK) epithelial cells (11). When cultured on microporous polycarbonate filters (Transwell, Costar, Cambridge, MA), MDCK cells will develop into monolayers mimicking the mucosal epithelium (11). When these cells reach confluence, tight junctions will be established between the cells, and free diffusion of solutes across the cell monolayer will be markedly inhibited. Tight junction formation can be monitored by measuring the transepithelial electrical resistance (TEER) across the cell monolayers. In Figure 1, MDCK cells were seeded at 2 X 104 cells per well in Transwells (0.4 p pore size) as described previously. TEER and 14C-sucrose transport were measured daily. To determine 14C-sucrose... 

Evaluation of the epithelial integrity can be performed by measuring the transepithelial electrical resistance (TEER). TEER values ranging from 150 ohms.cm2 up to 600 ohms.cm2 have been reported. An alternative method for assessing the monolayer integrity is to monitor the flux of hydrophilic marker molecules that pass the monolayers by the paracellular route (e.g., mannitol, Na-fluorescein, or atenolol). 

Most studies of the local actions of opioids on the intestinal mucosa have utilized muscle-stripped sheets of ileal mucosa with attached submucosa mounted in Ussing flux chambers. Peptidase-resistant enkephalin derivatives such as DPDPE decrease short-circuit current, an electrical measure of active transepithelial ion transport, across isolated mucosal sheets from the guinea pig ileum [46,127,128], rabbit ileum [129-131], mouse jejunum [132], and pig distal jejunum/ileum [133]. This effect, which occurs after the application of opioid agonists to the serosal aspect of epithelial sheets, is due to an increase in electroneutral salt absorption and a decrease in electrogenic chloride secretion [46,132,133], In contrast to enkephalin derivatives, opiate alkaloids have limited effects on active transepithelial transport of ions [69]. Pretreat-... 

Sutton, S.C. Forbes, A.E. Cargill, R. Hochman, J.H. LeCluyse, E.L. Simultaneous in vitro measurement of intestinal tissue permeability and transepithelial electrical-resistance (teer) using sweetana grass diffusion cells. Pharm. Res. 1992, 9, 316-319. 

The transepithelial electrical resistance measures predominantly the permeability of tight junctions for small ionic solutes. A partial disruption of tight junctions would not be detected by changes in permeability but by a drop in transepithelial resistance, which is reflected by an asymptotic relationship of... 

This buffer is used in both the unidirectional (permeability) and the bidirectional (Efflux, Section 4.3.2). In the permeability assay, NCEs are placed into the apical compartment of the Transwell. Duplicate samples are taken immediately after compound addition from the apical compartment (zero time) and then after 2h from both the apical and basolateral compartments for LC-MS/MS analysis. The integrity of the monolayer is confirmed by the measurement of the transepithelial electrical resistance (TEER), which must be above a certain limit to be used for transport experiments. In addition, with each experiment a transcellular and a paracellular marker are included for quality control. 

Knowles MR, Carson JL, Collier AM, Gatzy JT, Boucher RC. Measurements of nasal transepithelial electric potential differences in normal human subjects in vivo. Am Rev Respir Dis 1981 124 484. 

In particular barrier systems such as the blood-brain barrier (BBB) are characterized by the so-called transepithelial electrical resistance (TEER). The TEER is considered an important measure of function and quality of tight junctions which are formed between endothelial cells making up the barrier. CThanges in TEER may indicate leakage due to toxic side effects of drugs or may be a desired effect of a drug that is to pass the BBB in order to treat a disease within the central nervous system. Also, TEER is routinely measured to establish proper function of a barrier system (BBB, gut) prior to the tests of drug permeability. 

Transepithelial electrical resistance (TEER) measurements and transport smdies implied that CS/y-PGA NPs can be effective as an insulin carrier only in a limited area of the intestinal lumen where the pH values are close to the p/iTa of chitosan. So, a pH-responsive nanoparticle system was self-assembled by TMC and y-PGA for oral delivery of insulin. In contrast, TMC(40% Degree of Quatemisation) / y-PGA NPs may be a suitable carrier for transmucosal delivery of insulin within the entire intestinal tract. The loading efficiency and loading content of insulin in TMC/ y-PGA NPs were 73.8 2.9% and 23.5 2.1%, respectively. TMC/y-PGA NPs had superior stability in a broader pH range to CS/y-PGA NPs the in vitro release profiles of insulin from both test nanoparticles were significantly affected by their stability at distinct pH environments. TEER experiments showed that TMC/y-PGA NPs were able to open the tight junctions between Caco-2 cells, and this was further confirmed by confocal microscopy [66]. 

Fig. 1. Endogenous electric fields at epithelial wounds, (a) Schematic showing electric current flow (arrows) driven out the wound site by the transepithelial potential difference. (b) Small cut on human finger tip (/efl) and vibrating probe measuring current at the wound site (right), (c) Electrical currents at human finger wound, (b, c) are modified from (6).

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