Intracellular mechanisms involved in leukotriene C4-stimulated adhesion of U-937 cells.

Leukotrienes C4 and D4 (LTC4 and LTD4) stimulated, 5- to 6-fold, the adhesion of the monoblastoid cell line U-937 to plastic. Half-maximal effects were observed around 1 nM. Leukotrienes E4 and B4 (LTE4 and LTB4) were less effective. The adhesive response to LTC4 was inhibited by pertussis toxin and was completely dependent on the presence of extracellular Ca2+. The LTC4-stimulated increases in inositol-phosphates and in intracellular Ca(2+)-concentration were insensitive to pertussis toxin. Activation of leukocyte adhesion is a novel action of cysteinyl-leukotrienes and the present study suggests that control of U-937-cell adhesion by LTC4 involves two pathways; one pertussis toxin insensitive pathway regulating intracellular Ca2+ in a manner partly dependent on extracellular Ca2+ and one pertussis toxin sensitive pathway not concerned with Cai(2+)-regulation.