Fractional Clearance for Verapamil N-Demethylation in the Isolated Rat Liver Preparation

The hemodynamic properties of the hepatic vascular bed of the isolated rat liver preparation have been studied by the use of flow-pressure diagrams in experiments involving as a perfusate either whole blood or cell-free rat plasma under an oxygen partial pressure of 2.5 atm. Either perfusion medium yields a nonlinear flow-pressure diagram of sigmoid shape approaching a straight line through the origin at perfusion pressures slightly above physiological ones. Data are also reported concerning change of liver weight with perfusion pressure of the isolated organ. These, together with previously reported results of radiocolloid uptake studies, are incorporated into a representation of the hepatic vascular bed in terms of a population of parallel vascular channels having critical opening pressures distributed between 7 and 13 cm of plasma. The distribution function is described and its bearing upon liver function in relation to liver blood flow is briefly discussed.

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Circulatory Pathways in the Rat Liver as Revealed by P32 Chromic Phosphate Colloid Uptake in the Isolated Perfused Liver Preparation

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1956.184.3.593 ◽

1956 ◽

Vol 184 (3) ◽

pp. 593-598 ◽

Cited By ~ 54

Author(s):

Ralph W. Brauer ◽

G. F. Leong ◽

R. F. McElroy ◽

R. J. Holloway

Keyword(s):

Blood Flow ◽

Rat Liver ◽

Transit Time ◽

Mean Transit Time ◽

Total Activity ◽

Theoretical Treatment ◽

Perfusion Rate ◽

Isolated Rat Liver ◽

Liver Preparation ◽

Isolated Rat

P32-labeled chromic phosphate colloid disappears from the circulation of the isolated rat liver preparation according to a single exponential term of time. A small nonextracted contaminant, less than 3% of the total activity is also detected. At comparable blood flow rates the colloid is extracted about as completely by the isolated liver preparation as by the liver in situ in the intact animal. The efficiency with which chromic phosphate colloid is removed from perfusate passing through the isolated rat liver decreases with increasing perfusion rate. If whole blood is used as a perfusate, the efficiency of colloid extraction is almost twice as high as it is if rat blood plasma is employed, even if adequate oxygenation of the tissue is assured by high oxygen partial pressures in the latter series. A theoretical treatment of these results is given in terms of first order reaction kinetics. Agreement of experimental results with this theory at perfusion rates greater than 2 cc/gm/min. indicates that the rate of chromic phosphate colloid extraction is a function of plasma concentration of the colloid, and that the extraction efficiency for a given perfusate varies as a function of the mean transit time of perfusate through the liver. Deviations from the predictions of the theory occur at low perfusion rates, and are discussed in the light of the above concepts. A decrease of the ratio of transit time to perfusion rate under these conditions suggests a decrease in the number of channels open to blood flow at low perfusion pressures.

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