Van der Graaf P H, Schoemaker R C
Leiden/Amsterdam Center for Drug Research, Division of Pharmacology, The Netherlands.
J Pharmacol Toxicol Methods. 1999 Apr-Jun;41(2-3):107-15. doi: 10.1016/s1056-8719(99)00026-x.
We have developed a fitting procedure, based on nonlinear mixed effect modelling and original work by Richards (1959, J Exp Botany 10, 290-300), to describe the degree of asymmetry of concentration-effect E/[A] curves and analysed the shape of E/[A] curves obtained with alpha1-adrenoceptor agonists in rat aorta. The four-parameter Richards model provided a significantly better fit of the data than the standard logistic/Hill model for all ligands investigated, which implies that E/[A] curves were asymmetrical. With the exception of ST 587, the asymmetry parameter (delta) tended toward zero and the Richards model could be replaced without significant loss of goodness-of-fit by the three-parameter, asymmetrical Gompertz model. The alpha1-adrenoceptor antagonist, prazosin (10 nM), had no effect on the asymmetry of the noradrenaline E/[A] curve but significantly increased the slope at the point of inflection. In contrast, pretreatment with the irreversible antagonist, phenoxybenzamine (60 nM), produced a shift of the delta estimate for noradrenaline from zero to unity, indicating a change from an asymmetrical to a symmetrical curve. Therefore, detailed statistical analysis of E/[A] curve asymmetry demonstrates that alpha1-adrenoceptors in rat aorta do not operate as a homogenous one-receptor-one-transducer system. This conclusion could not have been reached by either an analysis with the standard logistic/Hill model or visual inspection of experimental data. Overall, the curve-fitting analysis developed in this study provides a quantitative and sensitive measure of asymmetry and a novel method for the objective discrimination of agonist action on the basis of curve shape. The method is generally applicable to other pharmacological assays and provides a new tool in receptor classification studies.
我们基于非线性混合效应建模以及理查兹（1959年，《实验植物学杂志》10卷，290 - 300页）的原创工作，开发了一种拟合程序，用于描述浓度 - 效应E/[A]曲线的不对称程度，并分析了用α1 - 肾上腺素能受体激动剂在大鼠主动脉中获得的E/[A]曲线的形状。对于所有研究的配体，四参数理查兹模型对数据的拟合明显优于标准逻辑斯蒂/希尔模型，这意味着E/[A]曲线是不对称的。除了ST 587外，不对称参数（δ）趋于零，并且三参数不对称冈珀茨模型可以替代理查兹模型，而不会显著损失拟合优度。α1 - 肾上腺素能受体拮抗剂哌唑嗪（10 nM）对去甲肾上腺素E/[A]曲线的不对称性没有影响，但显著增加了拐点处的斜率。相反，用不可逆拮抗剂酚苄明（60 nM）预处理后，去甲肾上腺素的δ估计值从零变为1，表明曲线从不对称变为对称。因此，对E/[A]曲线不对称性的详细统计分析表明，大鼠主动脉中的α1 - 肾上腺素能受体并非作为一个同质的单受体 - 单转导系统起作用。通过标准逻辑斯蒂/希尔模型分析或实验数据的目视检查都无法得出这一结论。总体而言，本研究中开发的曲线拟合分析提供了一种定量且灵敏的不对称性测量方法，以及一种基于曲线形状客观区分激动剂作用的新方法。该方法普遍适用于其他药理学测定，并为受体分类研究提供了一种新工具。
