Lucas M L
Am J Physiol. 1984 Nov;247(5 Pt 1):G463-7. doi: 10.1152/ajpgi.1984.247.5.G463.
The flux ratio equation used to describe intestinal weak electrolyte absorption in terms of a three-compartment model, with an intermediate compartment of distinctive pH, was examined in detail. This took the form of fitting the function to experimental data from the literature, using several different parameter sets. Within wide limits, estimation of intermediate compartment pH is seen to be arbitrary due to redundancy in the model. Several pairs of pH values can satisfactorily fit experimental data. Inspection of the function reveals that it contains four basic submodels whose distinct identity depend on whether or not pH2 greater than pH, and which of the two membranes in series has the highest discrimination between ionized and non-ionized forms. Further analysis of the function reveals that it provides an infinite but bounded set of values for intermediate compartment pH. The model is therefore redundant, nonlinear function fitting reveals ill conditioning, and estimates of pH2 from the present model cannot be regarded as definitive.
详细研究了用于根据三室模型描述肠道弱电解质吸收的通量比方程，该模型具有独特pH值的中间室。这采取了使用几个不同参数集将函数拟合到文献中的实验数据的形式。在很宽的范围内，由于模型中的冗余，中间室pH值的估计被认为是任意的。几对pH值可以令人满意地拟合实验数据。对该函数的检查表明，它包含四个基本子模型，其独特的特性取决于pH2是否大于pH，以及串联的两个膜中哪一个对离子化和非离子化形式具有最高的区分度。对该函数的进一步分析表明，它为中间室pH值提供了一个无限但有界的值集。因此，该模型是冗余的，非线性函数拟合显示出病态，并且从当前模型中估计的pH2不能被视为确定的。
