KINETICS OF UPTAKE AND METABOLISM BY ENDOTHELIAL CELL FROM INDICATOR DILUTION DATA.

We have developed an organ model based on events which occur at the capillary level, the principal site of substrate uptake. This model is mathematically equivalent to the case wherein the substrate is hydrolysed by enzyme distributed along the luminal surface of the endothelial cells. In addition, the balance equation can include binding of the substrate to plasma proteins via an equilibrium reaction. Solution of the balance equation provides time-varying substrate concentrations along the length of the capillaries. To obtain an organ model from the results of the capillary balance equation, we have assumed a random coupling of the capillaries and conducting vessels of the lung. If the bolus at the inlet to the capillaries is adequately dispersed relative to the capillary transit time distribution, a simple analytical method can be used for estimating the Michaelis-Menten parameters of the saturable transport or cell surface hydrolysis processes from the multiple indicator dilution saturable transport or cell surface hydrolysis processes from the multiple indicator dilution data.