Amat C, Puchal A, Planas J M, Moretó M
Dep. Ciències Fisiològiques Humanes i de la Nutrició, Facultat de Farmàcia, Universitat de Barcelona, Spain.
Rev Esp Fisiol. 1992 Sep;48(3):171-6.
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.
5周龄和13周龄鸡的近端盲肠通过两种对Na⁺需求不同的可饱和途径摄取L-脯氨酸（Pro）。我们研究了在无Na⁺条件下孵育的盲肠段中Pro流入的动力学特性，并测试了HgCl₂对摄取过程的影响。实验采用体外外翻肠囊法进行。通过非线性回归分析估算动力学参数。在存在HgCl₂的情况下孵育的组织中，1分钟的Pro通量符合一条直线，表明一个不依赖Na⁺的可饱和成分受到抑制。5周龄和13周龄鸡的估计Kd值相同，分别为0.023±0.001和0.027±0.001微升·毫克⁻¹·分钟⁻¹。对HgCl₂敏感的通量符合米氏双曲线，Km值相似，5周龄时为4.85±1.86，13周龄时为9.47±3.0毫摩尔/升。然而，5周龄鸡的Vmax*（0.662±0.053纳摩尔·毫克⁻¹·分钟⁻¹）高于13周龄鸡（0.420±0.039），这与之前的结果一致。目前的数据进一步支持了鸡近端盲肠中存在一种不依赖Na⁺的L-脯氨酸载体，该载体可被HgCl₂抑制。
