Search results for "testi"
showing 10 items of 4607 documents
Partially competitive inhibition of intestinal baclofen absorption by beta-alanine, a nonessential dietary aminoacid.
1991
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: Vm = 11.22 mM h-1; Km = 7.42 mM; Ki = 2.4…
Digestion and absorption rates of [3H]-oleic acid and [14C]-triolein do not differ in rats fed heated (-) and (+) gossypol cottonseed and soybean flo…
1998
This study was conducted to compare in vivo the acute effects of heated (+) and (-) gossypol cottonseed flours with those of soybean flour on lipid digestion and absorption in growing rats. Rats were fed by gastric intubation mixed [ 3 H]-oleic acid and [ 14 C]-triolein with heated flours or without flour (control). Lipid digestion and absorption were determined for 6 h after meal intubation. Both radioactivities recovered in gastrointestinal tract were significantly higher in rats fed (+) gossypol cottonseed flour than in all other groups. The majority of both recovered radioactivities was found in stomach contents, then in stomach wall and finally in intestinal wall. The distribution of b…
Kinetics of the intestinal uptake of zinc acexamate in normal and zinc-depleted rats.
1990
Abstract The uptake of zinc as acexamic acid salt in the small intestine of the anaesthetized rat was shown to be a two-phase process in normal animals. The first phase is rapid mucosal binding which satisfies the Freundlich isotherm equation and which involves about 30 per cent of the initially perfused zinc. The second phase was characterized as an apparent absorption step which obeys Michaelis-Menten and first-order combined kinetics, with the following parameters: Vm = 6.51 mg h−1; Km = 2.96 mg; ka = 0.306 h−1. In largely non-saturated conditions, an apparent global rate constant of about 2.50 h−1 was calculated. No significant interference due to endogenous zinc excretion into the smal…
Intestinal absorption pathway of gamma-aminobutyric acid in rat small intestine.
1994
Intestinal absorption of gamma-aminobutyric acid (GABA), as a model compound for gamma-aminoacids, has not been extensively studied from the kinetic viewpoint. Since data from our laboratory suggested that some competition arises between intestinal absorption of beta-alanine and GABA and since our intent was to maintain the aqueous stagnant diffusion layer in order to approach absorption tests to in vivo physiological conditions, a rat jejunum in situ study was undertaken in order to gain an insight into the mechanism of GABA absorption. In the present paper, results from assays using isotonic perfusion solutions with starting GABA concentrations ranging from 1 to 50 mM are reported. They s…
Quantitative analysis of the effect of controlled-release formulation on nonlinear gastrointestinal absorption of P-glycoprotein substrate talinolol …
2020
Abstract Oral absorption of talinolol, a substrate of P-glycoprotein (P-gp), from a sustained-release (SR) formulation was reportedly decreased compared to that from an immediate-release (IR) formulation. The aim of this study was to predict and understand the effect of controlled-release formulation on the oral absorption of P-gp substrates by developing a physiologically based pharmacokinetic (PBPK) absorption model incorporating multiple kinetic parameters obtained from in vitro studies, using talinolol as a model substrate. Simulation analysis using the developed PBPK absorption model indicated that the clinically observed marked decrease in the plasma concentration of talinolol adminis…
Effect of simulated gastrointestinal digestion on plant sterols and their oxides in enriched beverages
2013
Abstract This study evaluates the bioaccessibility (percentage of soluble compound available for absorption) of plant sterols (PS) and their oxides (phytosterol oxidation products, POPs) after simulated gastrointestinal digestion in fruit (Fb), milk (M) and fruit-based milk beverages with (FbM a ) or without (FbM b ) tangerine juice. In beverages and their bioaccessible fraction (BF), campesterol, campestanol, stigmasterol, β-sitosterol and sitostanol were detected. Bioaccessibility of total PS ranged between 2.62 and 6.48%, FbM b yielding the highest value, followed by FbM a > Fb > M. Campesterol/campestanol were the most bioaccessible PS. Only oxides of β-sitosterol were detected in beve…
Evidence of competitive inhibition for the intestinal absorption of baclofen by phenylalanine
1996
Abstract Previous studies showed that the absorption of the antispastic drug baclofen, in the rat middle intestine, is inhibited by β-alanine, γ-aminobutyric acid (GABA) and leucine. It was concluded that baclofen intestinal transport was mediated, at least in part, by the β-, γ- and α-amino acid carriers. We therefore focused our next studies on the analysis of the possible inhibition of drug absorption by an aromatic α-amino acid model compound, phenylalanine. An in situ study in the rat small intestine was undertaken in order to evaluate the effect of phenylalanine on baclofen absorption and to establish the inhibition model. Assays using isotonic perfusion solutions of 0.5 mM baclofen w…
Optimized In Silico Modeling of Drug Absorption after Gastric Bypass: The Case of Metformin
2021
Bariatric surgery is an effective treatment for severe obesity and related comorbidities, such as type II diabetes. Gastric bypass surgery shortens the length of the intestine, possibly leading to altered drug absorption. Metformin, a first-line treatment for type II diabetes, has permeability-dependent drug absorption, which may be sensitive to intestinal anatomic changes during bypass surgery, including Roux-en-Y gastric bypass (RYGB). Previous computer simulation data indicate increased metformin absorption after RYGB. In this study, we experimentally determined the region-dependent permeability of metformin, using the rat single-pass intestinal perfusion method (SPIP), which we then imp…
Absorption of Drugs after Oral Administration
2007
After oral administration, drugs must be absorbed through the gastrointestinal tract to achieve the systemic circulation and exert their pharmacological effects. The successful formulation of an optimized oral drug delivery system requires a detailed consideration and a good understanding of the intestinal absorption process, its possibilities and limitations. This article gives an overview and update on the concepts, possibilities, and limitations of drug absorption after oral administration. Keywords: oral administration; drug absorption; oral drug delivery system; gastrointestinal tract; intestinal absorption
Two New Alternatives to the Conventional Arm-in-Cage Test for Assessing Topical Repellents
2021
Abstract European guidelines for testing attractant and repellent efficacy (i.e., Product type 19 [PT19]) have been in revision since 2017. A key topic of discussion is the current approach to evaluating topical repellents. The European Chemical Agency has stated field testing should be avoided because of mosquito-borne disease risks. However, the most common laboratory method, the arm-in-cage (AIC) test, may limit the reliable extrapolation of lab results to field conditions. This study’s main goal was to assess alternative laboratory methods for evaluating topical mosquito repellents that use mosquito landing rates more representative of those in the field. The study took place at three E…