Partially competitive inhibition of intestinal baclofen absorption by beta-alanine, a nonessential dietary aminoacid
✍ Scribed by A. Polache; J. M. Plá-delfina; M. Merino
- Publisher
- John Wiley and Sons
- Year
- 1991
- Tongue
- English
- Weight
- 626 KB
- Volume
- 12
- Category
- Article
- ISSN
- 0142-2782
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
In situ intestinal absorption of baclofen in the rat in the presence of beta‐alanine has been investigated. Through the perfusion of 0·50 mM baclofen solutions containing variable concentrations of the aminoacid (from 5 to 100 mM), a partially competitive inhibition of baclofen absorption was characterized: absorption rate pseudoconstants of the spasmolytic drug decrease as beta‐alanine concentration increases, until a limiting value is obtained (36·8 per cent of that found for baclofen alone). A computer method was developed in order to calculate parameters governing baclofen absorption in the presence of beta‐aminoacid, with the following results: V~m~ = 11·22 mM h^−1^; K~m~ = 7·42 mM; K~i~ = 2·45 mM; α = 2·78; r = 0·998. Kinetic absorption parameters for betaalanine in the presence of 0·50 mM baclofen were also assessed: V~m~ = 49·88 mM h^−1^; K~m~ = 12·16 mM; r = 0·998, which, as can be expected, do not significantly differ from those previously found in the absence of the spasmolytic. It is concluded that baclofen and beta‐alanine compete for the same intestinal carrier system, although the values of the interaction parameters, particularly K~t~, can be more or less biased due to the limitations of the procedure and/or to the existence of some other carrier system for absorption. Possible practical implications of this phenomenon are briefly discussed.