Bile salts mixed micelles

Muranishi, S., N. Muranishi, and H. Sezaki. 1979. Improvement of absolute bioavailability of normally poorly absorbed drugs Inducement of the intestinal absorption of streptomycin and gentamicin by lipid-bile salt mixed micelles in rat and rabbit. Int J Pharm 2 101. 

Muranishi, N., et al. 1980. Mechanism for the inducement of the intestinal absorption of poorly absorbed drugs by mixed micelles. I. Effects of various lipid-bile salt mixed micelles on the intestinal absorption of streptomycin in rat. Int J Pharm 4 271. 

Tokunaga, Y., S. Muranishi, and H. Sezaki. 1978. Enhanced intestinal permeability to macromolecules. I. Effect of monoolein-bile salts mixed micelles on the small intestinal absorption of heparin. J Pharmacobiodyn 1 28. 

Nichols JW and OzarowskiJ. Sizing of Lecithin-Bile Salt Mixed Micelles by Size-Exclusion High-Performance Liquid-Chromatography. Biochemistry 1990 29 4600-4606. 

Data on absorption of non-micellar lipids in the presence of bile salts is available from the study )y Knoebel [79]. The lymphatic transport of absorbed oleic acid and site of uptake from the intestinal lumen was measured in bile fistula rats. It was found that the concentration of bile salts in a continuous intraduodenal infusion did not affect the steady-state level of lipid appearing in the lymph until the bile salt concentration was as low as 1 mM, which represented a molar ratio of 20 1 of lipid to bile salt. In the case of infusates with relatively low concentrations of bile salts it was found that a larger part of the available surface area of the small intestine was utilized. The main conclusion is that lipids are equally well absorbed in vivo from non-micellar dispersions of lipids and bile salts as from solutions where the lipids are completely solubilized by bile salt mixed micelles. However, a detailed analysis of kinetics of uptake from non-micellar phases in vitro with isolated intestinal segments has not yet been done. 

MA Schwarz, K Raith, HH Ruettinger, G Dongowski, RHH Neubert. Investigations of interactions between drugs and mixed bile salt/lecithin micelles—a characterization by micellar affinity capillary electrophoresis. Part III. J Chro-matogr A 781 377-389, 1997. 

Patton, J.S. and Carey, M.C. 1981. Inhibition of human pancreatic lipase-colipase activity by mixed bile salt-phospholipid micelles. Am. J. Physiol. 241, G328-G336. 

Patton JS and Carey MC. Inhibition of Human Pancreatic Lipase-Colipase Activity by Mixed Bile Salt-Phospholipid Micelles. Am J Physiol 1981 241 G328-G336. 

L. J. Soloman, J. K. Embleton, C. W, Poulon. Solubilization od steroidal compounds by mixed bile salt/iccithin micelles. In P, Couvrier, D. Duchenc, I. Kalics, eds. Formulation of Poorly Available Drugs for Oral Administration. Paris Editions de same, 1996, pp 219-2,30. 

The electrophoretic mobilities of C-labeled cholic, deoxycholic, and chenodeoxycholic acid and their corresponding taurine and glycine conjugates were determined by Norman (42). The paper electrophoresis was performed in barbiturate buffer of ionic strength 0.1, pH 8.6, in an electric field of 7.5 V/cm for 3 hr. When 1 pg of each acid, as the sodium salt dissolved in 25 pi of water, was applied to the paper strips, the isotope determination after electrophoresis showed broad peaks all with a mean mobility similar to that of albumin or slightly lower. The electrophoretic mobilities of all of the bile acids were influenced by the concentration in the solution applied and presented difficulties in identifying bile acids in natural extracts. The migration of bile salt-lecithin micelles on paper electrophoresis has been reported by Shimura (43). The micelles were prepared by addition of lecithin to mixed bile salts, which may have also contained cholesterol. 

FIGURE 24.4 In the small intestine, fatty acids combine with bile salts in mixed micelles, which deliver fatty acids to epithelial cells that cover the intestinal villi. Triacylglycerols are formed within the epithelial cells. 

Irrespective of the physical form of the carotenoid in the plant tissue it needs to be dissolved directly into the bulk lipid phase (emulsion) and then into the mixed micelles formed from the emulsion droplets by the action of lipases and bile. Alternatively it can dissolve directly into the mixed micelles. The micelles then diffuse through the unstirred water layer covering the brush border of the enterocytes and dissociate, and the components are then absorbed. Although lipid absorption at this point is essentially complete, bile salts and sterols (cholesterol) may not be fully absorbed and are not wholly recovered more distally, some being lost into the large intestine. It is not known whether carotenoids incorporated into mixed micelles are fully or only partially absorbed. 

Clothier, Jr., J. G. and Tomellini, S. A., Chiral separation of veraprimil and related componds using micellar electrokinetic capillary chromatography with mixed micells of bile salt and polyoxyethylene ethers,. Chromatogr. A, 712, 179,1996. 

Highly insoluble molecules are in part transported in the GIT by partitioning into the mixed micelles injected into the lumen from the biliary duct in the duodenum (Fig. 2.3). Mixed micelles consist of a 4 1 mixture of bile salts and phospholipids (Fig. 7.13). In contrast, at the point of absorption in the BBB, highly insoluble molecules are transported by serum proteins. This distinction is expected to be important in in vitro assay modeling. The use of simulated intestinal fluids is appealing. 

Shao Z, Mitra AK (1994) Bile salt-fatty acid mixed micelles as nasal absorption promoters. III. Effects on nasal transport and enzymatic degradation of acyclovir prodrugs. Pharm Res 11 243-250. 

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