大鼠睾丸受体结合促性腺激素的动力学。采用非线性曲线拟合方法进行分析。

Kinetics of gonadotropin binding by receptors of the rat testis. Analysis by a nonlinear curve-fitting method.

作者信息

Ketelslegers J M, Knott G D, Catt K J

出版信息

Biochemistry. 1975 Jul 15;14(14):3075-83. doi: 10.1021/bi00685a006.

Abstract

The kinetics of the reaction between human chorionic gonadotropin (hCG) and specific gonadotropin receptors in the rat testis were determined at 24 and 37 degrees, over a wide range of hormone concentrations. Hormone concentrations were corrected for the binding activity of the (-125I)hCG tracer preparations. Analysis of the experimental data was performed with an interactive nonlinear curve fitting program, based upon the second-order chemical kinetic differential equation. The mean values for the association rate constant (k1) were 4.7 x 10-7 M-1 min-1 at 24 degrees, and 11.0 x 10-7 M-1 min-1 at 37 degrees. At both temperatures, the values of kl were independent of hormone concentration. Initial dissociation rates were consistent with first order kinetics, with dissociation rate constant (k2) of 1.7 x 10 minus -3 and 4.6 x 10 minus -3 min minus -1 at 24 and 37 degrees, respectively. When studied over longer periods at 24 degrees, the dissociation process appeared to be multiexponential. The kinetics of degradation of (-125I)hCG and receptors were determined at both temperatures, and a mathematical model was developed by modification of the second-order chemical kinetic differential equation to take these factors into account. The application of such a model to hCG kinetic binding data demonstrated that reactant degradation had little significant effect on the derivation of the association rate constant (k1), but caused significant overestimation of the dissociation rate constant (k2) values derived from association experiments. The model was also applied by computer simulation to a theoretical analysis of the effects of degradation of free hormone and receptor sites upon kinetic and steadystate binding data. By this method, the initial velocities of hormone binding were shown to be less affected by degradation than the steady-state levels of hormone-receptor complex. Also, reactant degradation in simulated steady-state experiments caused an underestimate of the apparent equilibrium association constant, but had relatively less effect on the determination of binding site concentration.

摘要

在24℃和37℃下，于广泛的激素浓度范围内，测定了人绒毛膜促性腺激素（hCG）与大鼠睾丸中特异性促性腺激素受体之间反应的动力学。针对（-125I）hCG示踪剂制剂的结合活性对激素浓度进行了校正。基于二阶化学动力学微分方程，使用交互式非线性曲线拟合程序对实验数据进行分析。在24℃时，缔合速率常数（k1）的平均值为4.7×10⁻⁷ M⁻¹ min⁻¹，在37℃时为11.0×10⁻⁷ M⁻¹ min⁻¹。在这两个温度下，k1的值均与激素浓度无关。初始解离速率符合一级动力学，在24℃和37℃时，解离速率常数（k2）分别为1.7×10⁻³和4.6×10⁻³ min⁻¹。当在24℃下进行更长时间研究时，解离过程似乎是多指数的。在这两个温度下均测定了（-125I）hCG和受体的降解动力学，并通过修改二阶化学动力学微分方程以考虑这些因素建立了一个数学模型。将这样一个模型应用于hCG动力学结合数据表明，反应物降解对缔合速率常数（k1）的推导影响不大，但会导致从缔合实验得出的解离速率常数（k2）值被显著高估。该模型还通过计算机模拟应用于对游离激素和受体位点降解对动力学和稳态结合数据影响的理论分析。通过这种方法，结果表明激素结合的初始速度受降解的影响小于激素 - 受体复合物的稳态水平。此外，模拟稳态实验中的反应物降解导致表观平衡缔合常数被低估，但对结合位点浓度的测定影响相对较小。