Summary
In anaesthetized rats, jejunal segments 30 cm in length were perfused (rates: 0.1, 0.2, 0.5 ml/min) with solutions containing antipyrine, salicylic acid, urea, l-lysine, l- and d-phenylalanine. The intraluminal concentration was determined approx. 10, 20, and 30 cm from the inflow cannula. The intraluminal concentration gradients were almost exponential and corresponded to the gradient predicted for a laminar flow through a solute-permeable circular tube. This gradient has a slightly greater curvature than the exponential one. Theoretical considerations showed that the logarithmic mean (C O−C Z/In(C O/C Z) of the in- and outflow concentration is the best average value for application in non-integrated absorption equations. This is also valid for the temporal concentration gradient after single administration of a substance into an intestinal segment.
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Winne, D., Markgraf, I. The longitudinal intraluminal concentration gradient in the perfused rat jejunum and the appropriate mean concentration for calculation of the absorption rate. Naunyn-Schmiedeberg's Arch. Pharmacol. 309, 271–279 (1979). https://doi.org/10.1007/BF00504760
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DOI: https://doi.org/10.1007/BF00504760