Unstirred Water Layers and Absorption Across The Intestinal Mucosa

Dietschy, John M.; Sallee, Verney L.; Wilson, Frederick A.

doi:10.1016/s0016-5085(19)33408-0

Cited by 137 publications

(31 citation statements)

References 2 publications

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“…Although many aspects of the complex kinetics of passage through membranes have been extensively studied (Renkin, 1954;Kedem & Katchalsky, 1958;Katchalsky & Kedem, 1962;Galey & Van Bruggen, 1970;Dietschy, Sallee & Wilson, 1971 ;Gary-Bobo & Solomon, 1971;Starzak, 1973;Stender, Kristensen & Skadhauge, 1973;Winne, 1973), the present state of the art does not seem to allow a strict mechanistic interpretation of the present results. This arises from the fact that theory and experiment seem to have been concerned with the diffusion and filtration of nearspherical molecules rather than with asymmetrical molecules such as inulin.…”

Section: Physical Considerationsmentioning

confidence: 82%

Passage of inulin andp-aminohippuric acid through artificial membranes: Implications for measurement of renal function

Middleton

1975

J. Membrain Biol.

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Diffusion of inulin and p-aminohippuric acid (PAH) in combined aqueous solution through artificial membranes was measured at room temperature and atmospheric pressure. The membranes had pore diameters of 26, 50, 100, 200, 250, 350, 510 or 990 A. The diffusion of PAH was only restricted with a pore size of 26 A, but inulin diffusion was restricted at 100 A. When diffusion of both solutes was unrestricted (pore diameter greater than or equal to 200 A), PAH diffused four times faster than inulin, and in restricted situations this ratio was even greater. The results of these diffusion studies allow the major and minor molecular dimensions of the solutes to be estimated. Filtration of the two solutes was studied in slowly flowing situations and also with increased temperature and pressure. Pore sizes required for unrestricted filtration were the same as for unrestricted diffusion but the passage ratio was reduced from 4 to 2. These results suggest strongly that two conditions are necessary if the glomerular filtration rate (GFR) of inulin is to equal the true GFR: membrane pore size must be at least 200 A and passage through the membranes must be by bulk transport.

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Section: Physical Considerationsmentioning

confidence: 82%

Passage of inulin andp-aminohippuric acid through artificial membranes: Implications for measurement of renal function

Middleton

1975

J. Membrain Biol.

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“…This question was answered by the experiments conducted by Dietschy and his colleagues [8][9][10]. These investigators found that the brush-border membrane of enterocytes is separated from the bulk aqueous phase in the intestinal lumen by an unstirred fluid layer.…”

Section: Why Is Micellar Solubilization So Important For Intestinal Fmentioning

confidence: 99%

Enterocyte fatty acid uptake and intestinal fatty acid-binding protein

Tso

Nauli

2004

Biochemical Society Transactions

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This article reviews our current understanding of the uptake of fatty acids by the enterocytes of the intestine. The micellar solubilization of fatty acids by bile salts and the factors regulating that process are discussed. The mechanism of how micellar solubilization of fatty acids promotes the uptake of fatty acids by enterocytes and their relative importance is reviewed. Additionally, discussion of the various fatty acid transporters located at the brush border membrane of the enterocytes is included. Finally, a summary of our current understanding of the function of fatty-acid-binding proteins inside enterocytes is provided.

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“…Although the specific absorption mechanisms have not been elucidated, the common role of the mixed micellar phase in solubilizing poorly water-soluble lipid digestion products and providing a concentration gradient for absorption of monomeric lipids is generally accepted. [36][37][38] Micelles are not absorbed intact, 39,40 and lipids are thought to be absorbed from a monomolecular intermicellar phase. 37 In support of the importance of the intermicellar phase, concentrations of cholesterol several times higher than the saturated aqueous solubility can be achieved in the intermicellar environment.…”

Section: Lipids and The Post-prandial Intestinal Environmentmentioning

confidence: 99%

Physicochemical and Physiological Mechanisms for the Effects of Food on Drug Absorption: The Role of Lipids and pH

Charman

Porter

Mithani

et al. 1997

Journal of Pharmaceutical Sciences

545

343

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Drugs are absorbed after oral administration as a consequence of a complex array of interactions between the drug, its formulation, and the gastrointestinal (GI) tract. The presence of food within the GI tract impacts significantly on transit profiles, pH, and its solubilization capacity. Consequently, food would be expected to affect the absorption of co-administered drugs when their physicochemical properties are sensitive to these changes. The physicochemical basis by which ingested food/lipids induce changes in the GI tract and influence drug absorption are reviewed. The process of lipid digestion is briefly reviewed and considered in the context of the absorption of poorly water-soluble drugs. The effect of food on GI pH is reviewed in terms of location (stomach, upper and lower small intestine) and the temporal relationship between pH and drug absorption. Case studies are presented in which postprandial changes in bioavailability are rationalized in terms of the sensitivity of the physicochemical properties of the administered drug to the altered GI environment.

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Unstirred Water Layers and Absorption Across The Intestinal Mucosa

Cited by 137 publications

References 2 publications

Passage of inulin andp-aminohippuric acid through artificial membranes: Implications for measurement of renal function

Passage of inulin andp-aminohippuric acid through artificial membranes: Implications for measurement of renal function

Enterocyte fatty acid uptake and intestinal fatty acid-binding protein

Physicochemical and Physiological Mechanisms for the Effects of Food on Drug Absorption: The Role of Lipids and pH

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