Absorption and Transportation

Drugs. Ttifluoromethyl-based pharmaceuticals had been limited to phenothiatine tranquilizers and benzothiadiazine 1,1-dioxide diuretics (qv). However, new dmgs have been developed (Table 11). One of the key properties of the CF group is its high lipophilicity it increases the Hpid solubiUty of the pharmaceutical and thus accelerates absorption and transport within the host organism. 

The absorption and transport processes of many of the phytochemicals present in food are complex and not fully understood, and prediction of their bioavailability is problematic. This is particularly true of the lipid-soluble phytochemicals. In this chapter the measurement of carotenoid bioavailability will be discussed. The carotenoids serve as an excellent example of where too little understanding of food structure, the complexity of their behaviour in foods and human tissues, and the nature and cause of widely different individual response to similar intakes, can lead to misinterpretation of study results and confusion in our understanding of the relevance of these (and other) compounds to human health. 

S Suzuki, WI Higuchi, NFH Ho. Theoretical model studies of drug absorption and transport in the gastrointestinal tract. I. J Pharm Sci 59 644-651, 1970. 

T. L. Bierer, N. R. Merchen, and J. W. Erdman, Comparative absorption and transport of five common carotenoids in preruminant calves, J. Nutr. 125 (1995) 1569-1577. 

Suzuki A, Higuchi WI and Ho NF (1970a) Theoretical Model Studies of Drug Absorption and Transport in the Gastrointestinal Tract. I. J Pharm Sc. 59 pp 644-651. 

Elbert KJ, Schafer UF, Schafers HJ, Kim KJ, Lee VHL, Lehr CM (1999) Mono-layers of human alveolar epithelial cells in primary culture for pulmonary absorption and transport studies. Pharm Res 16(5) 601-608... 

In the limit of a semi-infinite (thick) porous electrode with no gas-phase diffusion limitations, the chemical term Zhem reduces to an impedance reflecting co-limitation by oxygen absorption and transport. ... 

Lymph may also be of importance as a vehicle for facilitating absorption and transport of lipid-soluble substances but also of particles by specialized cells (M cells) in the gut-associated lymphoid tissue (GALT). 

Sixliultt ion acts in concert with other electrolytes, in particular K. to regulate the osmotic pressure and to maintain the appropriate water and pi I balance ot the body. Homeostatic control of these functions is accomplished by the lungs and kidneys inlereciing by way of the blood. Sodium is essential for glucose absorption and transport of other substances across cell membranes. It is also involved, as is KJ. ill transmitting nerve impulses and in muscle relaxation. Potassium ion acts as a catalyst in the intracellular fluid, in energy metabolism, and is required for carbohydrate and protein metabolism. 

Raouf Hamid, M., F. Shmela, and S.A. Metwally. 1985. Influence of capsaicin on drug absorption and transport across biological membranes. J Drug Res Egypt 16 67. 

As a rule, the highest concentrations of a poison are found at the site of administration. A large quantity of drug in the GI tract and liver indicates oral ingestion. The gastrointestinal (GI) tract may contain large amounts of unabsorbed toxicant. Cases that involve the oral administration of toxicants indicate analysis of GI contents. However, the presence of toxic material in the GI tract does not provide sufficient evidence that the agent is the cause of death. Absorption and transport of the toxicant to the site of action must be demonstrated. Blood and tissue analysis is necessary and would still be paramount. 

Homan, R. and Hamelehle, K.L. 1998. Phospholipase A2 relieves phosphatidylcholine inhibition of micellar cholesterol absorption and transport by human intestinal cell line Caco-2. J. Lipid Res. 39, 1197-1209. 

Hui, D.Y. and Howies, P.N. 2005. Molecular mechanisms of cholesterol absorption and transport in the intestine. Semin. Cell Dev. Biol. 16, 183-192. 

Bates, S.S., Tessier, A., Campbell, EG.C. and Buffle, J. (1982) Zinc absorption and transport by Chlamydomonas variabilis and Scenedesmus subspicatus (Chlorophyceae) grown in semicontinuous culture./. Phycol, 18, 521-529. 

Lipids, unlike many excipients, whether present in food or as discreet pharmaceutical additives, are processed both chemically and physically within the GIT before absorption and transport into the portal blood (or mesenteric lymph). Indeed, most of the effects mediated by formulation-based lipids or the lipid content of food are mediated by means of the products of lipid digestion—molecules that may exhibit very different physicochemical and physiological properties when compared with the initial excipient or food constituent. Therefore, although administered lipids have formulation properties in their own right, many of their effects are mediated by species that are produced after transformation or activation in the GIT. An understanding of the luminal and/or enterocyte-based processing pathways of lipids and lipid systems is therefore critical to the effective design of lipid-based delivery systems. 

R. Blomhoff P. Helgerud, S. Dueland, T. Berg, J. I. Pederson, K. R. Norum, and C. A. Drevon, Lymphatic absorption and transport of retinol and vitamin D-3 from rat intestine—evidence for different pathways, Biochim. Biophys. Acta. 772 109-116 (1984). 

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