Influence of Prostaglandin I 2 on Fibronectin‐Mediated Phagocytosis In Vivo and In Vitro

This study evaluated the effect of prostaglandin I 2 (PGI 2 )on fibronectin‐me‐ diated macrophage phagocytosis in vivo and in vitro. Phagocytosis measured in vivo in rats by the vascular clearance rate and hepatic localization of gelatinized sheep erythrocytes was inhibited in a dose‐dependent manner after intravenous administration of PGI 2 . Phagocytosis was assessed in vitro in terms of uptake of fibronectin‐dependent gelatinized sheep erythrocytes by monolayers of casein‐elicited rat peritoneal macrophages. Concentrations of 1 ng/ml PGI 2 or greater resulted in inhibition of particle internalization but not attachment to macrophages. This inhibitory effect was enhanced by amino‐ phylline, a phosphodiesterase inhibitor. PGI 2 increased cAMP levels and these were further increased in the presence of aminophylline. These data indicate that PGI 2 inhibits macrophage uptake of gelatinized particles and support the idea that this is mediated by increased intracellular levels of cyclic AMP. PGI 2 should thus be considered a potential etiologic factor in the phagocytic depression observed in association with thrombosis.