Rat intestinal cells

B. Evaluation of Cell Membrane Affinity In Vivo Interaction with Rat intestinal Cells... 

The rat intestinal cell line IEC-18 has been evaluated as a model to study small intestinal epithelial permeability. This cell line forms very leaky monolayers with TER of 50 n cm2 and permeability to mannitol of 8 x 10-6 cm s 1. The IEC-18 model was proposed to be a better model than the Caco-2 monolayers for evaluating the small intestinal paracellular permeation of hydrophilic molecules. However, the leakier paracellular pathway is related to the poor differentiation level of the cells and an undeveloped paracellular barrier lacking peri-junctional actin-belt. In addition, due to the poor differentiation the cells have minute expression of transporters and are therefore not useful for studies of carrier-mediated transport [82, 84]... 

The paracellular permeation pathway in the intestinal cell monolayer models is often limited. Therefore these models are not suitable for predicting permeability of paracellularly absorbed compounds. The average pore radius in Caco-2 cells (<6 A) is more representative of the colon than the small intestine (8-13 A)and paracellular transport can be up to 100-fold lower in Caco-2 cells than in the small intestine. Investigation of a rat intestinal cell line 2/4/Al, which forms polarized cell mono-layers and has an average pore radius (9 A) more representative of the small intestine, showed improved prediction of oral absorption for incompletely absorbed drugs [24, 25]. 

Walker, W. A., Cornell, R., Davenport, L. M., and Isselbacher, K. J., 1972, Macromolecular absorption mechanism of horesradish peroxidase uptake and transport in adult and neonatal rat intestine,/. Cell Biol. 54 195-205. 

The existence of biologically active metabolites of retinoic acid has been reported. Krishnamurthy et al. (1963) detected a fat-soluble metabolite of retinoic acid, which displayed biological activity in a rat curative assay, in the liver of chicks administered a 10-mg oral dose of the parent retinoid. Similarly, Wolf et al. (1963) reported that an intestinal metabolite, isolated from retinoid-deficient rats injected with labeled retinoic acid, was active in restoring to normal levels the mucopolysaccharide biosynthesis in retinoid-deficient rat intestinal cell-free particle suspensions. The same laboratory also described a decarboxy-lated metabolite of both retinol and retinoic acid that was isolated from the intestine of retinoid-deficient rats administered retinol or retinoic acid. This compound, which appeared to have both carboxyl and hydroxyl functional groups, was biologically active in a growth assay (Yagishita et al., 1964). In... 

LIU Y and HU m (2002) Absorption and metabolism of flavonoids in the caco-2 cell culture model and a perfused rat intestinal model. Drug Metab Dispos. 30 (4) 370-77. 

Group and Treatment Number of Rats Squamous Cell Hyperplasia Glandular Hyperplasia Intestinal Metaplasia... 

Although the above profusion of in vivo studies evidence their health potentialities, the problem of the bioavailabihty of proanthocyanidins supplied by dietary supplementation has still not been completely resolved since unequivocal evidence for absorption is missing so far [11]. However, studies carried out using radio-labelled procyanidins revealed that dimers and trimers may be absorbed by intestinal cells, whereas a recent study demonstrated that procyanidin oligomers are readily adsorbed in rats [55], while it has been shown that colon microflora may be able to degrade proanthocyanidins to low-molecular-weight aromatic compounds [56]. 

Production of Mucosal Damage 2.3.1.2.1 Cell culture Stimulated neutrophils are known to be cytotoxic to cells in vitro (Dull et al., 1987 Dallegri et al., 1990 Grisham et al., 1990b). Several in vitro systems have been used to demonstrate oxidative damage to intestinal cells. Xanthine/XO increased Cr release and decreased [ H]thymidine uptake by IEC-18 small intestinal epithelial cell monolayers in a dose-dependent manner (Ma et al., 1991). Rat enterocytes show decreased trypan blue exclusion and increased protein release when incubated with neutrophils stimulated... 

K0/w as measured in the rat intestine [15,16], As with other examples that are available, as K0/w increases, the rate of absorption increases. One very extensive study [17-19] has examined in depth the physicochemical factors governing nonelectrolyte permeability for several hundred compounds. This study employed an in vitro preparation of rabbit gallbladder, an organ whose mucosal surface is lined by epithelial cells. The... 

R Hober, J Hober. Experiments on the absorption of organic solutes in the small intestine of rats. J Cell Comp Physiol 10 401 122, 1937. 

The absorption of short-chain weak acids in the rat intestine, as a function of pH, does not appear to conform to the pH partition hypothesis [44]. Similar anomalies were found with weak bases [77]. The apparent pKa values observed in the absorp-tion-pH curve were shifted to higher values for acids and to lower values for bases, compared with the true pKa values. Such deviations could be explained by the effect of an acid layer on the apical side of cells, the so-called acid pH microclimate [44,70,73,76-84],... 

The P-C isomer selectivity seems to be tissue-specific a preferential uptake of the all-trans isomer was shown in hepatic stellate HSC-T6 cells and in cell-free system from rat liver microsomes, but not in endothelial EAHY cells or U937 monocyte-macrophages (During et al., 2002). When Caco-2 cells were incubated with only 9-cis P-C, all -trans P-C did not increase in cells or in the basolateral medium, indicating that there is no cis-trans isomerization occurring in intestinal cells. Thus, the isomerization of 9-cis P-C observed in vivo (You et al., 1996) could take place in the... 

Several of the postulated roles for nematode-secreted AChEs assume that they gain access to the intestinal mucosa. Several possibilities exist for transport of parasite AChE across the epithelial cell barrier, such as (i) utilization of existing pathways for receptor-mediated transcytosis (ii) a paracellular route facilitated by parasite-secreted proteases as observed for a bacterial elastase (Azghani et al., 1993) and (iii) increased paracellular permeability resulting from inflammatory events in the mucosa. We consider the latter suggestion most likely, as this has been duplicated by ex vivo perfusion with rat mast cell protease II (Scudamore et al., 1995). Moreover, cholinergic stimulation attenuates epithelial barrier properties to macromolecules in rat ileal crypts (Phillips et al., 1987). 

The mechanisms whereby mast cells enhance host protection to H. polygyms and T. spiralis (and whether these are related to the leak-lesion hypothesis) have not yet been fully defined. Certainly, mast cells contribute to intestinal inflammation during infection through the secretion of a range of cytokines (Gordon et al., 1990) and vasoactive substances (see above). In addition, the release of mast cell proteases are known to increase enterocyte permeability to macromolecules in the rat intestine (Scudamore et al., 1995) and regulate epithelial cell functions at other mucosal sites (Cairns and Walls, 1996). 

Stadnyk, A.W., Sisson, G.R. and Waterhouse, C.C.M. (1995) Ida is constitutively expressed in the rat intestinal epithelial cell line IEC-6. Experimental Cell Research 220, 298-303. 

Figure 8.2 Rat duodenal cells divide in the crypts of Lieberktihn and differentiate while migrating to the villus tips within approximately 48 h. The crypt cells take up iron from the blood, and are thereby able to sense the body s state of iron repletion. They migrate to the villus tips where this information determines their iron absorption capacity from the intestinal lumen. Adapted from Schumann et al., 1999, by permission of Blackwell Science.

Conditionally immortalised cell line derived from foetal rat intestine... 

Some laboratories have found an alternative to the short-term cultures by using cell lines other than Caco-2 cells. The most popular of these is Madin-Darby canine kidney (MDCK) cells, an epithelial cell line from the dog kidney. MDCK cells have been suggested to perform as well as Caco-2 cells in studies of passive drug permeability [56]. These cells have also been used to optimise the conditions for studies of low-solubility drugs [53]. However, as noted previously, the active transport processes of this cell line can be quite different to those of Caco-2 cells [28-30], Another cell line that only requires short-term culture is 2/4/A1, which is a conditionally immortalised rat intestinal epithelial cell line [86]. The 2/4/A1 cell line is discussed in Section 4.3.2.2 below. 

Artursson, P., Ungell, A.-L., Lofroth, J.-E., Selective paracellular permeability in two models of intestinal absorption cultured monolayers of human intestinal epithelial cells and rat intestinal segments, Pharm. Res. 1993, 30, 1123-1129. 

Collett, A., Higgs, N. B., Sims, E., Rowland, M., Warhurst, G., Modulation of the permeability of H2 receptor antagonists cimetidine and ranitidine by P-glycoprotein in rat intestine and the human colonic cell line Caco-2, J. Pharmacol. Exp. Ther. 1999, 288, 171-178. 

Fraga, S., M. P. Serrao, and P. Soares-da-Silva. The L-3,4-dihydroxy-phenylalanine transporter in human and rat epithelial intestinal cells is a type 2 hetero amino add exchanger. Eur. J. Pharmacol. 2002, 441, 127—135. 

The uptake of radiocerium by intestinal lining cells is not unique but may be expected to occur in similar chemical compounds that form colloids or large complexes within the intestine (Sullivan, 1966). Macromolecules are known to be easily absorbed by the intestinal cells of newborn animals through the process of pinocytosis (Clark, 1959). Polyvinylpyrrolidone (PVP) has been shown to be taken into the intestinal cells of rats less than 18 days old (Clarke and Hardy, 1969). 

The PVP accumulated in large supranuclear vacuoles and, like immune globulins, remained there until the cells were sloughed. This pattern bears a marked similarity to radiocerium uptake in the intestinal cells of suckling rats. 

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