Active efflux pump

In principle there is no cross-resistance among the individual vinca alkaloids. However cells which are multidrug-resistant due to an activated efflux pump may display cross-resistance to vinca alkaloids, the epipodophyllotoxins, anthracyclines. 

Explosion of the compound from the cell usually through active efflux pumps... 

Active efflux pump removing antibiotic which passes into the cell. 

Reduced drug accumulation, by decreasing the permeability and uptake and/or increasing active efflux (pumping out) of the drug across the cell membrane. 

Biocide efflux must also be considered in the pseudomonads. For example, one mechanism of resistance of Ps. aeruginosa to the bisphenoltriclosan involves an active efflux pump. 

DiOC6 (3) is rapidly removed from the cells that have active efflux pump (P glycoprotein), such as stem cells or multi-drug resistant tumor cells, which may simulate collapse of AW,. 

Active efflux pumps are existing for example for Na" " in maize (Schubert and Lau-chli 1990) and for Ca " in wheat roots (Olbe and Sommarin 1991). They prevent the development of too-high concentrations in root cells. 

These are just some examples that demonstrate the complexity of the processes involved in intestinal absorption other parameters that need to be taken into consideration when studying intestinal transport include transepithelial electrical resistance (TEER), active efflux pumps (such as P-gp), passive transcellular and paracellular diffusion. 

Isken and de Bont conducted experiments to determine whether the solvent tolerant Pseudomonas putida S12 was able to export toluene by monitoring the accumulation of labeled toluene in the cells. Toluene-adapted cells were able to export toluene from their membranes whereas the non-adapted cells were not Furthermore, it was observed that in the presence of energy coupling inhibitors, toluene accumulation was the same as in the non-adapted cells. The amount of toluene in the cell was concluded to be kept at a low level by an active efflux system. The presence of a toluene-efflux system is supported by genetic research." " The pump has a striking resemblance to multidrug-efflux systems. Active efflux pumps for solvents have also been detected in other Pseudomonas strains. ... 

The combined intrinsic activities of different efflux pumps play a major role for the intrinsic resistance of Gram-negative bacteria to macrolides and oxazolidi-nones as well as to the intrinsic resistance of Pseudomonas aeruginosa against a broad range of disinfectants and antibiotics. 

In some cases, catechins can also act in synergistic mode when used in association with currently used antibiotic molecules (Table 2). EGCG exhibited synergy with /3-lactams. Sudano Roccaro et al. [73] found that this compound is able to reverse tetracycline resistance in Staphylococcus epidermidis and S. aureus isolates. This synergistic interaction has been explained by inhibition of tetracycline efflux pump activity in microbial cells resulting in an... 

In microbes without a permeability barrier, or when the barrier fails, a mechanism must be in place to export metals from the cytoplasm. These active transport systems involve energy-dependent, membrane-bound efflux pumps that can be encoded by either chromosomal- or plasmid-borne genes. Active transport is the most well-studied metal resistance mechanism. Some of these include the ars operon for exporting arsenic from E. coli, the cad system for exporting cadmium from Staphylococcus aureus, and the cop operon for removing excess copper from Enterococcus hiraeP i9A0... 

The use of Caco-2 cell monolayers has gained in popularity as an in vivo human absorption surrogate moreover, the monolayers are generally accepted as a primary absorption screening tool by several pharmaceutical companies [10]. However, Caco-2 cell permeability measurements exhibit certain limitations due to the mechanisms involved. Both passive and active pathways exist active transport tends to increase the absorption across the cells and, since Caco-2 cells overexpress the P-glycoprotein (P-gp) efflux pump, the absorption of some compounds across these cells may be underestimated. 

Hamilton KO, Backstrom G, Yazdanian MA, Audus KL (2001) P-glycoprotein efflux pump expression and activity in Calu-3 cells. J Pharm Sci 90(5) 647-658. 

P-gp) play an active role, and some of these function quite effectively as efflux pumps. One can, therefore, envisage a situation where brain efflux of the pyridinium intermediate competes with in situ activation by hydrolysis. 

Chaudhary, P. M., and Roninson, 1. B. (1991) Expression and activity of P-glycoprotein, a multidrug efflux pump, in human hematopoietic stem cells. Cell. 66, 85-94. 

---