Effect of ethanol on amino acid absorption across in vivo rat intestine

The acute effect of ethanol on amino acid absorption across the in vivo rat intestine was studied using single-pass continuous perfusion and recirculation techniques. The single-pass steady-state perfusion was used to examine the effect on the entire small intestine and recirculation perfusion to examine the effect on short intestinal segments and to limit ethanol absorption. Unlike the in vitro findings of other investigators, ethanol does not cause inhibition of net amino acid absorption in vivo unless the alcohol is perfused in 2 M or higher concentrations. The inhibition that is observed at these concentrations is very likely due to severe injury and shedding of intestinal cells as evidenced by an increased recovery of DNA in the perfusates. The findings suggest that acute ethanol administration, in concentrations that are comparable to those found in the upper intestines of humans after the ingestion of moderate doses of alcohol, does not have a prominent effect on amino acid absorption across the in situ rat intestine. Under these conditions, the ethanol inhibition of active absorption is masked by enhanced diffusion of the amino acids across the intestine.

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Acute and neonatal capsaicin treatment inhibit jejunal amino acid absorption through a Na+-dependent mechanism

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1997.272.4.g815 ◽

1997 ◽

Vol 272 (4) ◽

pp. G815-G821 ◽

Cited By ~ 3

Author(s):

K. A. Barada ◽

S. S. Dika ◽

S. F. Atweh ◽

N. E. Saade ◽

C. F. Nassar

Keyword(s):

Amino Acid ◽

Intestinal Epithelial ◽

Primary Afferent ◽

Acid Absorption ◽

Amino Acid Absorption ◽

Afferent Fibers ◽

Dependent Component ◽

Primary Afferent Fibers

It has recently been shown that capsaicin inhibits alanine absorption in rat jejunum via mechanisms that involve intestinal capsaicin-sensitive primary afferent (CSPA) fibers. This study provides further evidence that the effect of capsaicin is neurally mediated and demonstrates that CSPA fibers regulate Na+-dependent amino acid absorption. In vivo, basal alanine absorption in rats neonatally treated with capsaicin was reduced by 35% below control. Furthermore, intraluminal perfusion of 400 microM capsaicin reduced jejunal alanine absorption by 31% in sham rats but had no significant effect in rats neonatally treated with capsaicin. In vitro, capsaicin significantly reduced uptake of alanine and proline by jejunal strips but had no effect on uptake of lysine. Tetrodotoxin (0.2 microM) partially blocked the effects of capsaicin but did not itself affect alanine absorption. Capsaicin reduced unidirectional mucosal-to-serosal alanine (1 mM) influx by 33%, an effect that becomes significant after 5 min of preincubation with capsaicin. Neonatal capsaicin treatment reduced basal alanine influx in jejunal strips by 37%; however, preincubation of these strips with capsaicin had no significant effect. Kinetic analysis of alanine steady-state uptake and influx by jejunal strips incubated with capsaicin revealed that capsaicin reduced the Na+-dependent component of alanine influx into intestinal epithelial cells. Long-term sensory denervation by capsaicin also decreased the Na+-dependent component of alanine absorption. These data suggest that intestinal capsaicin-sensitive primary afferent fibers regulate Na+-dependent amino acid absorption.

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Drug–nutrient interactions: inhibition of amino acid intestinal absorption by fluoxetine

British Journal Of Nutrition ◽

10.1079/bjn19980074 ◽

1998 ◽

Vol 79 (5) ◽

pp. 439-446 ◽

Cited By ~ 3

Author(s):

Elena Urdaneta ◽

Isabel Idoate ◽

Jesús Larralde

Keyword(s):

Amino Acid ◽

Basolateral Membrane ◽

Membrane Vesicles ◽

Sugar Absorption ◽

Acid Absorption ◽

Leucine Uptake ◽

Amino Acid Absorption ◽

Dependent Transport

Fluoxetine is one of the most widely used antidepressants and nowadays it is also being used to manage obesity problems. In our laboratory we demonstrated that the drug inhibited sugar absorption (Monteiro et al. 1993). The aim of the present work was to determine the effect of fluoxetine on intestinal leucine absorption. Using a procedure of successive absorptions in vivo the drug diminished amino acid absorption by 30% (P < 0.001). Experiments in vitro in isolated jejunum also revealed a reduction in leucine uptake of 37% (P < 0.001). In both cases fluoxetine only affected mediated transport without altering diffusion. In a preparation enriched in basolateral membrane, fluoxetine inhibited the Na+,K+-ATPase (EC 3.6.1.37) activity (55%; P < 0.001) in a non-competitive manner with an inhibition constant (Ki) value of 0.92 mm. Leucine uptake by brush-border membrane vesicles was diminished by the drug (a reduction of 48% was observed at 30s, P < 0.001); only the apical Na+-dependent transport system of the amino acid was modified and the inhibition was non-competitive. Leucine uptake in the presence of lysine indicated that transporter B was involved. These results suggest that fluoxetine reduces leucine absorption by its action on the basolateral and apical membrane of the enterocyte; the nutritional status of the patients under drug treatment may be affected as neutral amino acid absorption is decreased.

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