Ståhle L, Segersvärd S, Ungerstedt U
Dept. of Pharmacology, Karolinska Institutet, Stockholm, Sweden.
J Pharmacol Methods. 1991 Mar;25(1):41-52. doi: 10.1016/0160-5402(91)90021-v.
In vitro models simulating tissues were used to test the validity of three methods for determining the free concentration of drugs and endogenous compounds in the extracellular space by means of microdialysis. Theophylline was used as a model substance. Recovery is defined as the proportion of compounds extracted from the medium surrounding the probe. The water recovery method is the use of recovery, determined in a water solution, to estimate concentrations in other media. This method was shown to underestimate the surrounding concentration when the effective rate of diffusion is smaller in the other medium than in water. The difference method measures the net transport over the dialysis membrane at varying concentrations in the perfusion medium. The point of equilibrium, where no net transport takes place, is used to estimate the surrounding concentration. The perfusion rate method involves two phases. In the first phase (calibration), surrounding media with different diffusion characteristics were used as tissue models. The amount recovered at different perfusion rates was measured and a multivariate regression method was used to calculate a mathematical model. In the second phase, the mathematical model was used to predict the concentration in the surrounding medium in new experiments. The two latter methods gave satisfactory predictions of the surrounding concentrations. Protein binding did not affect the methods. It is concluded that the difference method and the perfusion rate method may be used to estimate the in vivo concentration of drugs and endogenous compounds.
使用模拟组织的体外模型来测试通过微透析测定细胞外空间中药物和内源性化合物游离浓度的三种方法的有效性。以茶碱作为模型物质。回收率定义为从探针周围介质中提取的化合物比例。水回收率方法是利用在水溶液中测定的回收率来估算其他介质中的浓度。当其他介质中的有效扩散速率低于水中的有效扩散速率时，该方法会低估周围浓度。差异法测量在灌注介质中不同浓度下透析膜上的净转运。利用不发生净转运的平衡点来估算周围浓度。灌注速率法包括两个阶段。在第一阶段（校准），使用具有不同扩散特性的周围介质作为组织模型。测量不同灌注速率下回收的量，并使用多元回归方法计算数学模型。在第二阶段，在新的实验中使用该数学模型预测周围介质中的浓度。后两种方法对周围浓度给出了令人满意的预测。蛋白质结合不影响这些方法。结论是差异法和灌注速率法可用于估算药物和内源性化合物的体内浓度。
