Co-transporters

The rate of CO transport from the bulk gas into the gas and liquid films is as follows ... 

Several other conditions can provoke this reverse pump type of release. One is when the transmembrane ionic gradient is reversed. Experimentally this is achieved by reducing extracellular Na+. Because the neuronal uptake of monoamines from the synapse by the transporter requires co-transport of Na+ and Cl , reversing the ionic gradient (so that the Na+ concentration is lower outside, than inside, the terminals) will drive the transporter in the wrong direction. Such carrier-mediated release could explain the massive Ca +-independent release of noradrenaline during ischaemia which increases intracellular Na+ concentration and reduces intracellular K+. 

Rivera, C, Voipio, J, Payne, JA, Ruusuvuori, E, Lahtinen, H, Lamsa, K, Pirvola, U, Saarma, M and Kaila, K (1999) The K+/CU co-transporter KCC2 renders GABA hyperpolarizing during neuronal maturation. Nature 397 251-255. 

Opiates and various derivatives are commonly used to treat diarrhea, partly because they inhibit electrolyte secretion (Suzuki et al., 2000 Tumberg, 1983). Other phytochemicals counter the secretory responses to cholera toxin (Oi et al., 2002). An example would be the decreased chloride secretion caused by proanthocyanide and the ability to inhibit the secretory diarrhea caused by cholera toxin, but only if administered first (Hor et al., 1995). In the light of the co-transport of water and electrolytes by carriers of glucose... 

Brandsch, M., Miyamoto, Y., Ganapathy, V., Leibach, F. H., Expression and protein C-dependent regulation of peptide/H+ co-transport system in the Caco-2 human colon carcinoma cell line, Biochem. J. 1994, 299, 253-260. 

Wu, X., L. R. Whitfield, and B. H. Stewart. Atorvastatin transport in the Caco-2 cell model contributions of P-glycoprotein and the proton-monocarboxylic acid co-transporter. Pharm. Res. 2000, 17, 209-215. 

Furosemide inhibits the sodium-potassium-dichloride (Na+, K+, 2C12 ) co-transporters that are located in the... 

The answers are 370-c, 371-d, 372-c. (Hardman, pp 697, 701, 705.) The loop diuretic ethacrynic acid has its site of action in the ascending limb of the loop of Henle. This drug inhibits the reabsorption of Na and Cl" by interfering with the Na+, K+, 2CL co-transport system. In addition, loop diuretics block the reabsorption of Mg and Ca from the renal tubular fluid into the blood in this segment of the nephron unit. 

Fig. 2. Schematic diagram of the stoichometry of ion flux coupling and the chloride channel activity of glutamate transporters. Glutamate is coupled to the co-transport of 3 Na+, 1K+, and the countertransport of 1 K+. In addition, glutamate and Na+ binding to the transporter activates an uncoupled chloride flux through the transporter.

Various forms of macro- and microelements differ in their ability to migrate and redistribute among the soil profile. The elements contained in clastic minerals are practically immobile. The elements, bound to finely dispersed clay minerals, are either co-transported with clay particles, or are involved in sorption-desorption processes. Part of the elements are found in concretions and also in very thin coating films of hydrated iron oxides some elements make a part of specially edaphic organic compounds. 

In a study by Krishnamoorthy et al.,4s indigenous or added water led to marked increases in CO conversion for 12.7 wt% Co/Si02. The authors suggest that the water effects do not arise from new pathways introduced by water, by scavenging effects of H20 on the concentration of site-blocking unreactive intermediates, or by removing significant CO transport restrictions. As a result, they were left with only the possibility that water influences the relative concentration of the active and inactive forms of carbon, present at low concentrations on Co surfaces. The mechanism by which such effects occur was unclear. 

Hacksell, I., Rigaud, J. L., Purhonen, P., Pourcher, T., Hebert, H. and Leblanc, G. (2002). Projection structure at 8A resolution of the melibiose permease, an Na-sugar co-transporter from Escherichia coli, EMBO J., 21, 3569-3574. 

These methods of solute transfer usually rely on a relatively low intracellular concentration of the solute of interest, so that it will readily diffuse into the cell down the electrochemical gradient (as in the case of ion channels). Alternatively, the solute may be moved into the cell using chemical energy derived from another solute moved in the same direction (co-transport) or opposite direction (countertransport) on the carrier protein (symporters and antiporters respectively). The transfer of the second solute is in turn dependent on an inward electrochemical gradient. Ultimately, these gradients are established by primary, energy-requiring solute pumps (e.g. ATPases), which, on most epithelia, are located on the basolateral/serosal membrane (see Section 5.2 for discussion of ATPases). 

Symporter. a secondary ion transporter that moves a solute against its electrochemical gradient by using energy derived from the movement of another solute in the same direction across the cell membrane down its electrochemical gradient. Symporters are also called co-transporters. 

Hoffmann, E. K. (1982). Anion exchange and anion-cation co-transport systems in mammalian cells, Phil. Trans. R. Soc. Lond. B, 299, 519-535. 

Lafrance, P. and Lapointe, M. (1998). Mobilisation and co-transport of pyrene in the presence of Pseudomonas aeruginosa UG2 biosurfactants in sandy soil columns, Ground Wat. Monit. Remediat., 18, 139-147. 

Na+ co-transporter (symport) allows uptake of X (e.g. amino acid or glucose)... 

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