Platelet activating factor-induced pulmonary accumulation of 111Indium-oxine labelled neutrophils in anesthetized guinea pigs.

The thoracic accumulation of neutrophils labelled with 111Indium-oxine in response to infusion of platelet activating factor (PAF, 18 ng/kg/min x 5 min, i.v.) was studied using an automated isotope monitoring system (AIMSplus) in anesthetized guinea-pigs. Loss of cell associated radioactivity in vitro was less than 1% over 4 hr. Labelled neutrophils maintained their functional capacity (oxidative response to the cell stimulants N-formyl-L-methionine-L-leucine-L-phenylalanine and phorbol myristate acetate) and greater than 95% viability (ethidium bromide/acridine orange stain) in vitro. Total thoracic radioactivity increased significantly from baseline in response to PAF with a slight tachyphylaxia in the neutrophil-accumulation after a repeat PAF infusion. The highest ratios of radiolabel (tissue/blood) were found in the spleen much greater than liver greater than lung.