Genetic evidence for distinct roles of COX-1 and COX-2 in the immediate and delayed phases of prostaglandin synthesis in mast cells.

Activation of mast cells by aggregation of their high-affinity IgE receptors stimulates prostaglandin (PG) D(2) synthesis and secretion. An immediate phase of PGD(2) synthesis, complete within 30 min, is followed by a delayed, second phase of PGD(2) production that reaches a maximum 4 to 8 h after activation. Activation of mast cells from COX-2 (-/-) mice stimulates the release of PGD(2) during the first 30 min, whereas activation of mast cells from COX-1 (-/-) mice does not generate any PGD(2) in the first 2 h. On the other hand, COX-2 (-/-) cells do not participate in delayed phase of PGD(2) synthesis, while COX-1 (-/-) cells secrete low levels of PGD(2) between 2 and 4 h after activation. These data demonstrate that (i) the first phase of PG synthesis is COX-1 dependent and (ii) the second, delayed phase of PG synthesis is dependent on activation-induced synthesis and activity of COX-2. Copyright 1999 Academic Press.