O'Brasky J E, Mauro T, Crandall E D
J Appl Physiol Respir Environ Exerc Physiol. 1979 Nov;47(5):1079-83. doi: 10.1152/jappl.1979.47.5.1079.
pH equilibration after gas exchange in a systemic vascular bed was investigated using an isolated guinea pig liver preparation perfused with a blood-free Krebs-Ringer-bicarbonate solution. Effluent perfusate was withdrawn into a stopped-flow apparatus in which pH and temperature were continuously monitored. A decrease in pH of the perfusate after exit from the liver was observed. Addition of acetazolamide to inflowing perfusate had little effect on this fall in effluent fluid pH, while the addition of carbonic anhydrase completely abolished the decrease in pH. These results suggest that: 1) after the addition of metabolically produced CO2, the reaction CO2 leads to H2CO3 leads to H+ + HCO3- in the perfusate did not reach equilibrium during passage through the liver; 2) acetazolamide had little effect on the magnitude of the pH disequilibrium; and 3) carbonic anhydrase accelerated the reaction to equilibrium. We conclude that little or no catalysis of the conversion of perfusate CO2 to H2CO3 takes place within the hepatic circulation and that the presence of slow postcapillary blood pH changes in vivo may be dependent on the specific species and organ vascular bed from which the blood exited after participating in gas exchange.
使用灌注无血 Krebs-Ringer-碳酸氢盐溶液的豚鼠离体肝脏标本，研究了体循环血管床气体交换后的pH平衡。将流出的灌注液收集到停流装置中，在该装置中连续监测pH和温度。观察到灌注液流出肝脏后pH值下降。向流入的灌注液中添加乙酰唑胺对流出液pH值的下降影响不大，而添加碳酸酐酶则完全消除了pH值的下降。这些结果表明：1）在添加代谢产生的CO2后，灌注液中CO2→H2CO3→H⁺ + HCO₃⁻的反应在通过肝脏的过程中未达到平衡；2）乙酰唑胺对pH不平衡的程度影响不大；3）碳酸酐酶加速了反应达到平衡。我们得出结论，在肝循环中灌注液CO2向H2CO3的转化几乎没有或没有催化作用，并且体内毛细血管后血液pH缓慢变化的存在可能取决于参与气体交换后血液流出的特定物种和器官血管床。
