Wunder M A, Gros G
Zentrum Physiologie, Medizinische Hochschule, Hannover, Deutschland.
Isotopes Environ Health Stud. 1998;34(3):303-10. doi: 10.1080/10256019808234064.
A membrane inlet system to a mass spectrometer (MIMS) allows us to monitor the abundance of 18O in CO2 during the exchange of 18O between HCO3-, dissolved CO2 and H2O that occurs after dissolving 18O-labelled NaHCO3 in aqueous solution. Using a mathematical model we quantitate intracellular carbonic anhydrase activity and membrane permeabilities for HCO3-, CO2 and H2O of isolated cells or intact epithelia added to the solution. For these calculations it was necessary to determine (a) the relation between MS signal and [C18O16O], (b) MIMS response kinetics and (c) CO2 leakage during the experiment. The three parameters were determined by stepwise addition of HCl to HCO3- solution: (a) was found to be linear, (b) response times were 7.5 +/- 2s (10 degrees C), 4.5 +/- 1s (20 degrees C), 3.5 +/- 0.6s (37 degrees C), and (c) CO2 leakage was < 1/1000 s-1.
一种用于质谱仪的膜进样系统（MIMS）使我们能够在将18O标记的NaHCO3溶解于水溶液后，监测HCO3-、溶解的CO2和H2O之间发生的18O交换过程中CO2中18O的丰度。利用数学模型，我们可以对添加到溶液中的分离细胞或完整上皮细胞的细胞内碳酸酐酶活性以及HCO3-、CO2和H2O的膜通透性进行定量分析。为了进行这些计算，有必要确定：（a）质谱信号与[C18O16O]之间的关系；（b）MIMS响应动力学；以及（c）实验过程中的CO2泄漏情况。这三个参数通过向HCO3-溶液中逐步添加HCl来确定：（a）被发现呈线性关系；（b）响应时间在10℃时为7.5±2秒，20℃时为4.5±1秒，37℃时为3.5±0.6秒；（c）CO2泄漏率<1/1000 s-1。
