Physiologic distribution of colony-stimulating factor in vivo

Purified 1-cell colony-stimulating factor (CSF) was iodinated by several techniques and used to determine the physiologic distribution in vivo.Mice were injected i.v. or i.p. with 100,000 cpm; plasma and tissue radioactivity were monitored at intervals up to 6 hr.A complex plasma disappearance curve was observed after i.v.injection.There was a 80%-90% reduction in circulating radioactivity at 4 hr.This resulted from a biphasic pattern, in which the tV2 was 24-40 mm and 2-2.5 hr in the first and second phases, respectively.