Platelet activating factor‐induced pulmonary accumulation of 111 indium‐oxine labelled neutrophils in anesthetized guinea pigs

The thoracic accumulation of neutrophils labelled with 111 Indium‐oxine in response to infusion of platelet activating factor (PAF, 18 ng/kg/min × 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 >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 >>liver>lung.