Glycine transport by intestinal brush border vesicles of the amphibian Discoglossus pictus.
1. In order to determine the different components of glycine uptake by the intestine of the frog, Discoglossus pictus, we have used brush border membrane vesicles isolated by a classical precipitation technique. 2. Enzymatic tests showed that a good purification was obtained. The concentration ratio of alkaline phosphatase was 14.8. 3. Glycine entry in vesicles as a function of time, in presence or absence of sodium, indicated an overshoot which decreased when incubation time was prolonged. The overshoot was dependent on the presence of sodium. 4. The nature of the anion associated to sodium had little effect on glycine uptake. Nevertheless, chloride and thiocyanate appeared more efficient than glutarate. 5. The effect of transmembrane potential was studied by using valinomycin associated with a potassium gradient. The addition of this substance stimulated glycine transport by 43%. 6. The transport at different glycine concentrations showed two components: one non-saturable with weak affinity and the other saturable with strong affinity (Kt = 0.338 mM). 7. In conclusion, glycine transport by the brush border of D. pictus intestine presents a saturable component depending on sodium and on transmembrane electrical potential.
Physiology Laboratory of Nutrition, Faculty of Sciences, Tunis University, Tunisia.
D
D
Saidane
G
G
Boge
B
B
Tritar
G
G
Peres
D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D000838:Anions / Q000378:metabolism; D001001:Anura / Q000378:metabolism* / Q000502:physiology; D001692:Biological Transport; D004594:Electrophysiology; D005998:Glycine / Q000493:pharmacokinetics*; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000502:physiology; D008871:Microvilli / Q000378:metabolism; D009994:Osmolar Concentration; D012964:Sodium / Q000502:physiology; D013997:Time Factors
D000596:Amino Acids; D000838:Anions; D012964:Sodium; D005998:Glycine