Is lung sequestration of indium-111-labeled granulocytes organ specific?

Transient sequestration of polymorphonuclear leukocytes (PMN) in the normal lungs of animals occurred immediately following intravenous injection of 111In-labeled PMN. We investigated the organ specificity of this process. Equal amounts of homologous PMN, derived from the intravascular space and labeled with [111In]oxine, were infused either intravenously (i.v.) or intraarterially (i.a.) into pairs of rats. Changes in radioactivity emitted from three regions--representing lung, liver and spleen, and lower body--were determined from images during the following hour. A nonspecific character was demonstrated by the transient sequestration of activity in the lower body following i.a. infusions. However, the rate of initial clearance of activity (first 30 min) from the lungs of i.v.-infused rats was relatively slower than from the lower body of i.a.-infused rats. This suggests the presence of a lung-specific as well, which may be important for localization of PMN-related events to the lung.