Rat Jejunal perfusion

Biopharmaceutical classiLcation depends on both solubility and permeability of one drug. So, insoluble drugs with good permeability are clased as Class II drugs, and insoluble drugs with low 

It should be noted that the partition coafient is a constant. The apparent partition coetfnt of the protolytic forms of the drug substance, which obviously can vary as a function of pH, is deLned as the distribution coefcient (Q/w). Both logP and logD have been used widely as indications of lipophilicity of one drug. 

The methods commonly used for the measurement of partitiohoiBafts include the traditional shake-Lask method, HPLCJter-probe, and pH-metric techniques. These methods have been reviewed extensively (Avdeef, 1993). Dearden and Bresnen (1988) axzel Laboratory Procedure (GLP) recommendations on experimental procedures. Hersey et al. (1989) presented a method selection guide. In addition, several methods are available for partition.cissft calculations (Lipinski et al., 1997). 

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Tallkvist J, Tjalve H. 1994. Nickel absorption from perfused rat jejunal and ileal segments. Pharmacol Toxicol 75 233-243. 

The jejunal lumen of rat was perfused in Krebs-Ringer phosphate buffer (pH7.4) containing ImM glucose in the presence or absence of the non-sugar fraction or BS-1. 

Figure 9.6 The dependence of salicylic acid absorption on the net water flux (positive sign flow directed from the lumen and towards the blood) in the rat jejunal loop perfused with hypo-, iso- and hypertonic solutions at pH 6.2 and 2.2. The lines, mean values with 95% confidence limits (shaded areas), were calculated by means of the parameters determined by a kinetic model with the following constants concentration of salicylic acid in the perfusion solution 32.3 /

Fig. 23 Dependence of intestinal absorption on blood flow as reported by Winne and Remischovsky. All data are corrected to a concentration of 50 nmol/mL in the solution perfusing jejunal loops of rat intestine. Bracketed points indicate the 50% confidence intervals. (From Ref. 54.).

The efficient intestinal absorption of bile acids involves both active and passive absorption, but little information on the relative sites and mechanisms of absorption and on their contribution to the entire enterohepatic cycle of bile acids exists. Although the contribution of passive and active absorption of bile acids in the rat small intestine has been measured (20), no data are available for other species. The major site of absorption in all vertebrates appears to be the ileum, where an active transport site exists (14,15). Free bile acids are absorbed passively in the jejunum by nonionic diffusion, dihydroxy acids being absorbed more rapidly than trihydroxy acids (21,22). Perfusion studies in the human jejunum have suggested that glycine dihydroxy bile acids may be absorbed to some extent, and additional evidence for jejunal absorption of bile acids has been obtained in patients and animals with ileal resection (97,98). No information exists on the importance of jejunal bile acid absorption in health in man. Taurine-conjugated bile acids do not appear to be absorbed in the human jejunum (24). 

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