Jackson M J, Tai C Y, Steane J E
Am J Physiol. 1981 Mar;240(3):G191-8. doi: 10.1152/ajpgi.1981.240.3.G191.
The potential significance of ionized species in weak electrolyte absorption or secretion has been reexamined using a mathematical model that represents the epithelium as a system of parallel ion-permeable and ion-impermeable channels. An important determinant of weak electrolyte movement in this system is the ratio of ionized and nonionized permeabilities (Pi/Pni). This variable, which has been termed the discrimination coefficient, interacts with the degree of ionization in determining the contributions of ionized and nonionized species to the transepithelial movement of a weak electrolyte. Calculations based on the model suggest that ionized species may contribute significantly to the absorption or secretion of many common weak electrolytes. It is concluded that the frequently made assumption that ionized species do not contribute significantly to transepithelial movements of weak electrolytes in the alimentary tract is not generally valid. Further work is required to delineate the quantitative determinants of discrimination in alimentary epithelia, and two methods for evaluation of epithelial discrimination coefficients are described.
利用一个数学模型重新审视了离子化物种在弱电解质吸收或分泌中的潜在意义，该模型将上皮组织视为一个由平行的离子通透通道和离子不通透通道组成的系统。该系统中弱电解质移动的一个重要决定因素是离子化和非离子化渗透率的比值（Pi/Pni）。这个变量被称为辨别系数，在确定离子化和非离子化物种对弱电解质跨上皮移动的贡献时，它与电离程度相互作用。基于该模型的计算表明，离子化物种可能对许多常见弱电解质的吸收或分泌有显著贡献。得出的结论是，通常认为离子化物种对消化道中弱电解质的跨上皮移动贡献不大的假设一般是无效的。需要进一步开展工作来确定消化道上皮辨别能力的定量决定因素，并描述了两种评估上皮辨别系数的方法。
