Medium change amplifies mitogen-activated protein kinase-mediated prostaglandin E2 synthesis in Swiss 3T3 fibroblasts

In Swiss 3T3 fibroblasts, changing the culture medium prior to stimulation resulted in an augmentation of bradykinin-induced prostaglandin E-2 synthesis. The augmentation depended on the duration of the exposure to the fresh medium, with a maximum effect at 1 h. Fetal calf serum in the fresh medium was essential for augmented prostaglandin E-2 synthesis. The medium change slightly augmented the bradykinin-induced increase in intracellular free Ca'+ concentration and phosphoinositide hydrolysis with a different time course from that for prostaglandin E-2 synthesis. 4',5,7-Trihydroxyisoflavone (genistein) and 3,4-dihydroxybenzylidene-malononitrile (tyrphostin 23), inhibitors of tyrosine kinases, and 2'-amino-3'-methoxyflavone (PD98059), an inhibitor of mitogen-activated protein kinase (MAPK) kinase, attenuated the increase in prostaglandin E-2 synthesis. Bradykinin caused phosphorylation of cytosolic phospholipase A(2) and p42/p44 MAPK, which was augmented by the medium change. From the results, it is concluded that activation of MAPK and cycosolic phospholipase A(2) is involved in the augmentation of prostaglandin E-2 synthesis produced by the medium change. (C) 1998 Elsevier Science B.V. All rights reserved.