HgCl2 inhibition of Na-independent L-proline transport in chicken proximal cecum.
The proximal cecum of 5- and 13-wk-old chickens takes up L-proline (Pro) by two saturable pathways that differ in their requirement of Na+. The kinetic properties of Pro influx in cecal segments incubated in Na(+)-free conditions, have been studied and the effect of HgCl2 on the uptake process has been tested. Experiments were carried out using an in vitro everted-sleeve method. Kinetic parameters were estimated by nonlinear regression analysis. One min Pro fluxes in tissues incubated in presence of HgCl2 fit a straight line, indicating that a Na-independent saturable component was inhibited. Estimated Kd* values are the same in 5- and 13-wk-old chickens, 0.023 +/- 0.001 and 0.027 +/- 0.001 microliters.mg-1 x min-1, respectively. HgCl2-sensitive fluxes fit a Michaelis hyperbola, with similar Km* values, 4.85 +/- 1.86 (5-wk) and 9.47 +/- 3.0 (13-wk) mmol/l. However, Vmax* in 5-wk chickens (0.662 +/- 0.053 nmol.mg-1 x min-1) is higher than in 13-wk birds (0.420 +/- 0.039), in accordance with previous results. The present data give further support to the existence of a Na-independent L-proline carrier in the chicken proximal cecum which is inhibitable by HgCl2.
Amat
C
C
Dep. Ciències Fisiològiques Humanes i de la Nutrició, Facultat de Farmàcia, Universitat de Barcelona, Spain.
Puchal
A
A
Planas
J M
JM
Moretó
M
M
D000367:Age Factors; D026921:Amino Acid Transport Systems, Neutral; D000818:Animals; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002432:Cecum / Q000187:drug effects* / Q000378:metabolism; D002645:Chickens / Q000378:metabolism; D003864:Depression, Chemical; D007408:Intestinal Absorption / Q000187:drug effects*; D007700:Kinetics; D008297:Male; D008627:Mercuric Chloride / Q000494:pharmacology*; D011392:Proline / Q000378:metabolism*; D012964:Sodium / Q000502:physiology
D026921:Amino Acid Transport Systems, Neutral; D002352:Carrier Proteins; C041832:proline transport protein; D008627:Mercuric Chloride; D011392:Proline; D012964:Sodium