THE DISTRIBUTION OF MONOCYTES IN THE RAT

In the rat, labeled transfused monocytes initially leave the circulation with a halftime of 0.2 hr. They first collect on the walls of small vessels then migrate outward until equilibrium is established between the circulating pool and a large extravascular pool which contains about twenty-five times as many monocytes as the circulating blood. From this pool they leave randomly and irreversibly with a halftime of 14 hr. The spleen and lungs make up a large part of the pool and splenectomy reduces the size of the extravascular compartment and slows the rate of sequestration.