Chloride uptake

JA Bonanno, SD Klyce, EJ Cragoe Jr. (1989). Mechanism of chloride uptake in rabbit corneal epithelium. Am J Physiol 257 C290-C296. 

Figure 2. Sodium and chloride uptake across an idealised freshwater-adapted gill epithelium (chloride cell), which has the typical characteristics of ion-transporting epithelia in eukaryotes. In the example, the abundance of fixed negative charges (muco-proteins) in the unstirred layer may generate a Donnan potential (mucus positive with respect to the water) which is a major part of the net transepithelial potential (serosal positive with respect to water). Mucus also contains carbonic anhydrase (CA) which facilitates dissipation of the [H+] and [HCO(] to CO2, thus maintaining the concentration gradients for these counter ions which partly contribute to Na+ import (secondary transport), whilst the main driving force is derived from the electrogenic sodium pump (see the text for details). Large arrow indicates water flow...

Williams, E. M. and Eddy, F. B. (1986). Chloride uptake in fresh-water teleosts and its relationship to nitrite uptake and toxicity, J. Comp. Physiol. B, 156, 867-872. 

Stutts MJ, Cotton CU, Yankaskas JR, Cheng E, Knowles MR, Gatzy JT, Boucher RC (1985) Chloride uptake into cultured airway epithelial cells from cystic fibrosis patients and normal individuals. Proc Natl Acad Sci USA 82(19) 6677-6681. 

Bloomquist JR, Soderlund DM. 1985. Neurotoxic insecticides inhibit GABA independent chloride uptake by mouse brain vesicles. Biochem Biophys Res Commun 133 37-43. 

Ghiasuddin SM, Matsumura F. 1982. Inhibition of gamma-amino butyric acid (GABA)-induced chloride uptake by gamma-BHC-d heptachlor epoxide. Comp Biochem Physiol 73C 141-144. 

Block repolarization by inhibiting Na+, K+-ATPase Block GABA-stimulated chloride uptake... 

Delayed inactivation of channels in excitable tissnes, cansing repetitive firing and at high doses, depolarization Block GABA-stimnlated chloride uptake Muscle weakness, aching, and tenderness hypotonia... 

Fig. 4. Approximate structure of halorhodopsin, based on analogy with bacteriorhodopsin. Putative chloride channels are as indicated with inclined dotted cylinders. arglOS probably participates in chloride uptake arg200 probably participates in chloride release [50],...

FIGURE 2.51 A mechanism for sodium chloride uptake, as explained in four steps of increasing complexity (a) The sodium/proton exchanger, (b) The sodium/proton exchanger with catalysis of add production by carbonic anhydrase. (c) The sodium/proton exchanger with catalysis of acid production and utilization of bicarbonate by the bicarbonale/chioride exchanger, (d) The finished model for transport of sodium and chloride ions. 

The observed slight deactivation occurred in the first layer. Reasons are decrease of BET-surface area (200 ni /g to 100 in /g), chloride reception (maximum chloride uptake 0.66 w.-Z) and decrease of platinxim dispersion (STEM-pholography, fig. 1), Increase of chloride-content was highest in inlet-layer which was at lowest temperature during operation. 

The neuroexcitatory properties of toxaphene are due to its ability to reduce chloride uptake into neurons, leading to depolarization of the cells and hyperactivity. It is believed that toxaphene acts on the picrotoxin-binding site on the GABAa receptor. 

An inhibiting chemical slows the enzymatic metabolism of a toxic chemical. In this instance, if the uptaken chemical itself is the toxin, inhibition will slow the metabolism and intensify its action. If the metabolite of the absorbed xenobiotic is the toxic agent, inhibition will decrease the toxic affect. Vinyl chloride uptake in rats results in the lowering of cytochrome P450 and a corresponding loss of ability to metabolize other xenobiotics. Other inhibitors include diethyl maleate, which inhibits glutathione s-transferase and 1-aminobenzotriazole, which inhibits P450. 

Recent studies from our research group have demonstrated the presence of GABA and picrotoxinin receptors and the Cl channel complex in the central nervous system of American and German cockroaches (4,7) In the current study, avermectin was found to increase chloride uptake in the leg muscle cells of the American cockroach Avermectin may act as a presynaptic inhibitor by opening Cl channels of the GABA synapse so that the presynaptic membrane is not able to release an excitatory transmitter, or as a postsynaptic inhibitor by opening the chloride channel in the postsynaptic region ... 

Recent studies have grouped lindane with the cyclodienes on the basisLjaf its potent and stereospecific inhibition of [3H]DHPTX (.2,3) and [3DS]TBPS (4 J>) binding. However, the quantitative correlations between potency in the chloride flux assay, potency in the [3 >S]TBPS binding assay, and acute toxicity that were observed for the cyclodienes do not extend to lindane. Lindane was a very weak inhibitor of chloride uptake (I 1 mM J7). Inclusion of the data... 

The polychlorinated cage compounds mirex and chlordecone were very poor inhibitors of GABA-dependent chloride uptake, producing little or no. .inhibition at 100 yM (j ). These compounds also failed to inhibit s]TBPS binding at concentrations up to 10 yM (4). Thus, despite the potent inhibition of [3H]DHPTX binding in cockroach CNS preparation by chlordecone (3), it appears that these compounds act at sites other than the GABA receptor-ionophore complex in mammals. 

The avermectins have been shown to increase chloride conductance in invertebrate electrophysiological preparations (J, JA,25) and modulate the binding of several GABA receptor-ionophore ligands (9, 10), but the molecular mechanisms underlying their neurotoxicity remain poorly defined. Recently, Abalis e t al. (1 ) reported an avermectin Independent stimulation of chloride uptake in rat brain vesicles tnat... 

Figure 5 EffecJLs of abamectin (AM) at 3 PM in either the preincubation or °C1 uptake medium on basal chloride uptake and at 3 pM in the preincubation medium on uptake stimulated by GABA (100 PM), Ethanol (EtOH 1 pi) was the control for AM addition to the preincubation medium. Results are means + standard errors of total chloride uptake per mg protein from three experiments using different vesicle preparations (26),...

Figure 6, Effect of preincubation with different concentrations of abamectin on subsequent chloride flux stimulated by 100 pM GABA, Results are means + standard errors of normalized specific chloride uptake in three experiments using different vesicle preparations (26).

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