Influence of Prostaglandin I2 on Fibronectin-Mediated Phagocytosis In Vivo and In Vitro

Abstract

This study evaluated the effect of prostaglandin I2 (PGI2) on fibronectin-mediated macrophage phagocytosis in vivo and in vitro. Phagocytosis measured in vivo in rats by the vascular clearance rate and hepatic localization gelatinized sheep erythrocytes was inhibited in a dose-dependent manner after intravenous administration of PGI2. 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 PGI2 or greater resulted in inhibition of particle internalization but not attachment to macrophages. This inhibitory effect was enhanced by aminophylline, a phosphodiesterase inhibitor. PGI2 increased cAMP levels and these were further increased in the presence of aminophylline. These data indicate that PGI2 inhibits macrophage uptake of gelatinized particles and support the idea that this is mediated by increased intracellular levels of cyclic AMP. PGI2 should thus be considered a potential etiologic factor in the phagocytic depression observed in association with thrombosis.