Marra Carlos A, Girón María Dolores, Suáre María Dolores
INIBIOLP Instituto de Investigaciones Bioquímicas de La Plata, CONICET-UNLP, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Argentina.
Lipids. 2002 Mar;37(3):273-83. doi: 10.1007/s11745-002-0891-5.
In this manuscript we report a study of the transport of FA in L6 muscle cells. Cultured L6 cells took up labeled FA (C10 to C20) as a linear function of time up to 15 min. Thereafter, the rate of uptake gradually declined although it persisted for at least 12 h after the addition of the substrate. Kinetic parameters (Km, Vm, and k(o)) were determined from a fitted Michaelis-Menten-type equation modified by a term for a saturable (linear) component of the measured total uptake. Vm values were different for some of the FA studied, and Km data showed significant differences between saturated and unsaturated FA. The maximal rate of uptake was observed at pH 7.40 for decanoate, palmitate, and eicosatrienoate. Uptake was significantly influenced when the pH of the incubation medium was changed. Experiments designed to study the influence of FA/albumin molar ratio indicated that Vm was dependent on the total (bound and free) concentration of the FA. A concentrative uptake was demonstrated in short-term experiments with an apparent plateau of 20 and 40 microM for palmitate and eicosatrienoate, respectively. A competitive inhibition was also observed between palmitate as substrate and the other FA. From our results we can postulate that the uptake of FA in L6 cells is the sum of passive diffusion plus a saturable component and that the rate of uptake is dependent on one (or more) protein structures, although their precise characteristics and functions remain to be elucidated.
在本论文中，我们报告了一项关于脂肪酸（FA）在L6肌肉细胞中转运的研究。培养的L6细胞摄取标记的脂肪酸（C10至C20），在长达15分钟的时间内呈时间的线性函数关系。此后，摄取速率逐渐下降，尽管在添加底物后至少持续12小时。动力学参数（Km、Vm和k(o)）由一个经过修改的米氏方程拟合确定，该方程加入了一个用于测量总摄取的可饱和（线性）成分的项。对于一些研究的脂肪酸，Vm值不同，并且Km数据显示饱和脂肪酸和不饱和脂肪酸之间存在显著差异。癸酸、棕榈酸和二十碳三烯酸在pH 7.40时观察到最大摄取速率。当孵育培养基的pH值改变时，摄取受到显著影响。旨在研究脂肪酸/白蛋白摩尔比影响的实验表明，Vm取决于脂肪酸的总（结合和游离）浓度。在短期实验中证实了棕榈酸和二十碳三烯酸分别有20和40 microM的明显平台期的浓缩摄取。还观察到底物棕榈酸与其他脂肪酸之间的竞争性抑制。从我们的结果可以推测，L6细胞中脂肪酸的摄取是被动扩散加上一个可饱和成分的总和，并且摄取速率取决于一种（或多种）蛋白质结构，尽管它们的确切特征和功能仍有待阐明。
