Crandall E D, O'Brasky J E
J Clin Invest. 1978 Sep;62(3):618-22. doi: 10.1172/JCI109168.
Isolated rat lungs were ventilated with air and perfused with a blood-free Krebs-Ringer bicarbonate solution under conditions of net CO2 elimination in the lung. Some of the effluent perfusate was drawn through a stop-flow pH electrode apparatus, arriving at the electrode within 4 s after passing through the pulmonary capillaries. pH and temperature of the fluid in the electrode chamber were continuously monitored both before and after withdrawal was suddenly stopped. Little or no change was observed in the pH of the perfusate after flow was stopped, despite the fact that CO2 was eliminated in the lung, suggesting that the conversion of H2CO3 to CO2 in the blood-free perfusion fluid was markedly accelerated and the rise in pH was complete by the time the perfusate reached the electrode. Because the effluent perfusate was shown to be free of carbonic anhydrase activity, the catalysis must have occurred during transit through the isolated lung. When acetazolamide was added to the perfusate, a rise in the pH of the perfusate after stopping flow was consistently seen. These results suggest that the carbonic anhydrase of isolated lungs accelerates the conversion of H2CO3 to CO2 and enhances COW elimination as perfusate passes through the pulmonary capillaries, and that the enzyme may be present on the capillary endothelial surface.
在肺净排出二氧化碳的条件下，对离体大鼠肺进行空气通气并用无血的 Krebs-Ringer 碳酸氢盐溶液灌注。部分流出的灌注液通过停流 pH 电极装置抽取，在通过肺毛细血管后 4 秒内到达电极。在突然停止抽取之前和之后，持续监测电极腔内液体的 pH 和温度。尽管肺中二氧化碳被排出，但停止流动后灌注液的 pH 几乎没有变化，这表明在无血灌注液中碳酸向二氧化碳的转化明显加速，并且在灌注液到达电极时 pH 的升高已完成。由于流出的灌注液显示没有碳酸酐酶活性，催化作用一定发生在通过离体肺的过程中。当向灌注液中加入乙酰唑胺时，停止流动后灌注液的 pH 持续升高。这些结果表明，离体肺的碳酸酐酶加速碳酸向二氧化碳的转化，并在灌注液通过肺毛细血管时增强二氧化碳的排出，并且该酶可能存在于毛细血管内皮表面。
