AJP - Endocrinology and Metabolism, Vol 253, Issue 6 E691-E700, Copyright © 1987 by American Physiological Society
Effect of sampling site on early kinetics of blood radioiodide and pertechnetate
M. T. Hays, L. J. Carr and J. M. Turrel
Veterans Administration Medical Center, Palo Alto 94304.
Radioiodide (I) and radiopertechnetate (TcO4) were sampled simultaneously
from left ventricle, right atrium, and femoral vein early after intravenous
injection to pentobarbital sodium-anesthetized cats. Concentrations of both
tracers in femoral vein blood was lower than in left ventricular (arterial)
blood, with rapid narrowing of the differences over 20 min and gradual
approach to steady state. Right atrial blood concentrations were
intermediate. When these data were fitted to three-compartment mamillary
models, representing blood and tissue pools, compartment size and kinetics
differed according to which sampling site was taken as representative of
each cat's blood. We have developed a model incorporating
subcompartmentalization of the blood with an exchange compartment
connecting to the pulmonary circulation as well as compartments exchanging
with peripheral sites. With the use of this model, all data sets fitted
well. The pulmonary exchange compartment and a large rapid exchange
compartment in the femoral vein drainage areas are essential to reconciling
the differences among sampling sites.
