[Effect of ascorbic acid on the intestinal transport of glycine in chick].
The effect of different doses of ascorbic acid on the absorptive functions of the gut has been investigated in chicks. The study describes evidence for the existence of a H+/glycine symport system in chick intestinal brush border, because in sodium-free conditions acidification of the apical medium with ascorbic acid causes a dose-dependent stimulation of glycine absorption. Under the above circumstances, potassium acts as a non-essential activator of H+-dependence glycine cotransport. Our results also suggest that glycine uptake is stimulated in a lesser degree by inward sodium gradient. Ascorbic acid stimulation of glycine uptake from K+- free sodium abundant media was diminished, when the dietary level of ascorbic acid was increased to 2000 mg in 1 kg of food. This may result from conformational change in the Na(-)-dependent glycine transporter protein that lowers glycine binding site affinity induced by the over-acidification of the gut lumen. In addition, there was a possible competition between sodium-dependent glycine and ascorbic acid transporters for sodium.
Basova
N A
NA
Berzinia
N I
NI
Markov
Iu G
IuG
D026905:Amino Acid Transport Systems / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects; D002645:Chickens / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005998:Glycine / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007421:Intestine, Small / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism
D026905:Amino Acid Transport Systems; D000975:Antioxidants; D012964:Sodium; D001205:Ascorbic Acid; D011188:Potassium; D005998:Glycine