Certain electron acceptors, such as TBO are reduced on the surface of the pulmonary endothelium upon passage through the lung. Since oxidoreductase catalysis is typically pH sensitive, and the redox potential of TBO is negatively correlated with pH, we measured the effect of pH on TBO reduction by the pulmonary endothelium. Isolated rabbit lungs were ventilated with different concentrations of CO2 producing a range in pH from 7.12 to 8.02. Boluses of TBO and a reference indicator (125I albumin) were injected into the pulmonary artery and their concentrations measured in the left atrium. Using this concentration data and a mathematical model based on multiple indicator dilution theory, Ek, a parameter representative of the product of the number of binding sites on the endothelial surface (E) and the reductase association rate constant (k), was estimated. Ek increased with pH according to: Ek = 9.0 exp (2.5 (pH-7.04)) Based solely on the redox potential of TBO, this result would be contrary to expectation. The positive correlation between TBO reduction and pH therefore suggests that the pH effect is on the transport of electrons across the endothelial plasma membrane rather than on the TBO redox potential.
|Original language||English (US)|
|State||Published - Dec 1 1997|
ASJC Scopus subject areas
- Molecular Biology