Abstract
Background: To maintain intracellular environment, pH is regulated by several acid-extruding membrane mechanisms. HCO3− plays important role in regulating intracellular pH and therefore simultaneous monitoring of extracellular pH and pCO2 leads to understand how the homeostasis are kept. Here, we developed pH microsensor system based on ion-sensitive field effect transistor (ISFET) which can detect pH and pCO2 changes in less than 1 microL solution and evaluated the metabolism in the immediate vicinity of endothelial cells of excised rabbit aorta. Materials and Methods: Two sensors were placed at the center of excised rabbit aorta, one was for pH monitoring and the other covered with CO2 permeable silicon tube for pCO2 monitoring. We used Tyrode solution buffered with NaHCO3 which was much more sensitive to pH change than blood. After circulation of this solution, we stopped the solution and monitored the time course of pH and pCO2 changes for 10 minutes. Results: pH and pCO2 were changed monotonically and saturated at 10 minutes. Changes of pCO2 at 10 minutes were significantly larger than that of pH (-0.76 ± 0.10 and -0.93 ± 0.09 respectively, n = 5, p < 0.05). Conclusion: Larger change in pCO2 compared to pH suggested secretion of alkaline, which should be HCO3−. Using chemical equilibrium of CO2, lactate, and bicarbonate, we found that the amount of bicarbonate ion secretion was ∼one-third of CO2 production. [Jpn J Physiol 55 Suppl:S96 (2005)]
