A chloride requirement for Na+-dependent amino-acid transport by brush border membrane vesicles isolated from the intestine of a Mediterranean teleost (Boops salpa).
The uptake of D-glucose, 2-aminoisobutyric acid and glycine was studied with intestinal brush border membrane vesicles of a marine herbivorous fish: Boops salpa. The uptake of these three substances is stimulated by an Na+ electrochemical gradient (Cout greater than Cin). For glucose, an increase of the electrical membrane potential generated by a concentration gradient of the liposoluble anion, SCN-, increases the Na+-dependent transport. This responsiveness to the membrane potential was confirmed by valinomycin. Differently from glucose, uptake of glycine and 2-aminoisobutyric acid requires, besides the Na+ gradient, the presence of Cl- on the external side of the vesicles. In the absence of Cl-, amino acid uptake is not stimulated by the Na+ gradient and is not influenced by an electrical membrane potential generated by SCN- gradient (Cout greater than Cin) or by a K+ diffusion potential (Cin greater than Cout). This Cl- requirement differs from the Na+ requirement, since a Cl- gradient (Cout greater than Cin) does not result in an accumulation of glycine or 2-aminoisobutyric acid similar to that produced by an Na+ gradient.
D000596:Amino Acids / Q000378:metabolism*; D000621:Aminoisobutyric Acids / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism*; D002712:Chlorides / Q000494:pharmacology*; D005399:Fishes; D005947:Glucose / Q000378:metabolism; D005998:Glycine / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism*; D007700:Kinetics; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology*
D000596:Amino Acids; D000621:Aminoisobutyric Acids; D002712:Chlorides; D012964:Sodium; D005947:Glucose; D005998:Glycine