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首页> 外文期刊>The Journal of Membrane Biology: An International Journal for Studies on the Structure, Function & Genesis of Biomembranes >Characterization of the erythrocyte sodium-lithium countertransporter: limitations and assumptions of traditional and kinetic methodologies.
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Characterization of the erythrocyte sodium-lithium countertransporter: limitations and assumptions of traditional and kinetic methodologies.

机译：红细胞钠-锂反向转运蛋白的表征：传统方法和动力学方法的局限性和假设。

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摘要

The present work examined the key elements featuring in the various methods used to characterize the erythrocyte sodium-lithium countertransport. Effects of medium composition on lithium efflux were investigated in 20 subjects. Mean lithium efflux (mmol Li/l RBC.h) into a 150 mM sodium medium was significantly higher than efflux into a revised sodium-rich medium (149 mM) containing 1 mM Mg (0.335 +/- 0.100 vs. 0.298 +/- 0.085 respectively; P < 0.03). Mean lithium efflux into sodium-free media where sodium had been entirely replaced by magnesium, was significantly lower than efflux into a choline-based medium containing only 1 mM magnesium (0.088 +/- 0.027 vs. 0.109 +/- 0.034 respectively; P = 0.03). Sodium-lithium countertransport activity and the transporter's kinetic profile were measured simultaneously in 35 subjects using traditional choline-based and kinetic methodologies. There was a significant correlation between countertransport activity and maximal rate of turnover (Vmax) (r = 0.62; P < 0.001); Vmax values were consistently greater than their corresponding countertransport activities (P < 0.001). On subdividing the subject group into tertiles based on the Michaelis-Menten constant (km) values (mM), < 75, 75-150 and > 150, the slopes of the regression lines for each group diminished progressively (0.64, 0.49 and 0.23 respectively), correlations within each group remained significant (P < 0.001, P < 0.001 and P < 0.02). No significant correlation was found between km values and countertransport activity (r = 0.035; P = NS). Increasing the number of points representing sodium concentrations within the range 0-150 mM, improved the confidence in the emerging estimates of Vmax and km obtained by linear transformation. Comparison of kinetic data derived using four different analytical methods (two linear transformations, a nonlinear regression and a statistical method), showed no significant differences between the estimates yielded for either Vmax (P = 0.88. NS) or km (P = 0.92, NS). This study has highlighted the critical roles of assay conditions and derivation techniques used when measuring sodium-lithium countertransport, emphasizing the need for standardization of the methodology.
机译：本工作检查了用于表征红细胞钠-锂反向转运的各种方法中的关键要素。在20名受试者中研究了培养基成分对锂外排的影响。进入150 mM钠培养基的平均锂流出量（mmol Li / l RBC.h）显着高于经过修正的含1 mM Mg的富钠培养基（149 mM）的流出量（0.335 +/- 0.100 vs. 0.298 +/-分别为0.085; P <0.03）。钠已完全被镁替代的无钠培养基中的平均锂流出量显着低于仅含1 mM镁的胆碱基培养基中的流出量（分别为0.088 +/- 0.027和0.109 +/- 0.034; P = 0.03）。使用传统的基于胆碱和动力学的方法，同时测量了35位受试者的钠-锂逆转运活性和转运蛋白的动力学特征。反转运活动与最大周转率（Vmax）之间存在显着相关性（r = 0.62; P <0.001）; Vmax值始终大于其相应的逆转运活性（P <0.001）。根据Michaelis-Menten常数（km）值（mM）将<75、75-150和> 150分为三分位数时，每组的回归线斜率逐渐减小（分别为0.64、0.49和0.23 ），各组之间的相关性仍显着（P <0.001，P <0.001和P <0.02）。 km值与逆转运活性之间未发现显着相关性（r = 0.035; P = NS）。增加表示钠浓度在0-150 mM范围内的点的数量，提高了对通过线性变换获得的Vmax和km的最新估计值的信心。使用四种不同的分析方法（两种线性变换，非线性回归和统计方法）得出的动力学数据的比较表明，对于Vmax（P = 0.88。NS）或km（P = 0.92，NS）得出的估计值之间没有显着差异。 ）。这项研究突出了测定条件和衍生技术在测量钠-锂反向转运时的关键作用，强调了方法标准化的必要性。

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