TY - JOUR
T1 - A mathematical model of indicator extraction by the pulmonary endothelium via saturation kinetics
AU - Bronikowski, Thomas A.
AU - Dawson, Christopher A.
AU - Linehan, John H.
AU - Rickaby, David A.
N1 - Funding Information:
This study wus supportedb y the VeteransA dministration und Research Grant HL 24349 from the National Heurt, Lung and Blood Institute. The authors also wish to express their appreciation to Mary McDermott and CatherineA . Waltherf or typingt his manuscript.
PY - 1982/10
Y1 - 1982/10
N2 - When a bolus containing a nonpermeating indicator and an indicator which permeates the endothelial cell membrane by a saturable process is injected into the blood flowing into the lung, the instantaneous extraction ratio curves measured in the pulmonary venous outflow are asymmetric with respect to the nonpermeating indicator curve. If the bolus contains a sufficient quantity of the permeating indicator that the capillary concentration begins to saturate the transfort mechanism, the extraction ratio curves are concave upward as well. The purpose of this study was to determine whether a mathematical model which represents endothelial extraction by Michaelis-Menten kinetics could explain the time variation in the instantaneous extraction ratio curves. The venous concentration curves were assumed to be the result of the endothelial transfort and distributed capillary input and transit times. In addition, we evaluated a method for estimating the kinetic parameters (Km and Vmax) of the saturable transfort process in such an organ. The results of simulations indicate that the important features of the data can be reproduced by the model, and that useful estimates of the kinetic parameters will be obtained from linear multiple regression analysis of the venous concentration curves if the standard deviation of the capillary input time distribution is not less than that of the capillary transit time distribution.
AB - When a bolus containing a nonpermeating indicator and an indicator which permeates the endothelial cell membrane by a saturable process is injected into the blood flowing into the lung, the instantaneous extraction ratio curves measured in the pulmonary venous outflow are asymmetric with respect to the nonpermeating indicator curve. If the bolus contains a sufficient quantity of the permeating indicator that the capillary concentration begins to saturate the transfort mechanism, the extraction ratio curves are concave upward as well. The purpose of this study was to determine whether a mathematical model which represents endothelial extraction by Michaelis-Menten kinetics could explain the time variation in the instantaneous extraction ratio curves. The venous concentration curves were assumed to be the result of the endothelial transfort and distributed capillary input and transit times. In addition, we evaluated a method for estimating the kinetic parameters (Km and Vmax) of the saturable transfort process in such an organ. The results of simulations indicate that the important features of the data can be reproduced by the model, and that useful estimates of the kinetic parameters will be obtained from linear multiple regression analysis of the venous concentration curves if the standard deviation of the capillary input time distribution is not less than that of the capillary transit time distribution.
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U2 - 10.1016/0025-5564(82)90005-0
DO - 10.1016/0025-5564(82)90005-0
M3 - Article
AN - SCOPUS:0020331885
SN - 0025-5564
VL - 61
SP - 237
EP - 266
JO - Mathematical Biosciences
JF - Mathematical Biosciences
IS - 2
ER -