title: Regulation of prostaglandin H synthase activity in dog urothelial cells.
abstract: TPA regulation of prostaglandin H synthase activity in primary and subcultured dog urothelial cells was investigated. Previous studies have demonstrated an early (0-2 hr) increase in PGE2 synthesis mediated by TPA which is dependent upon release of endogenous arachidonic acid by a phospholipase-mediated pathway. In this study, prostaglandin H synthase activity was assessed directly with microsomes and indirectly after addition of exogenous arachidonic acid at a maximum effective concentration (100 microM) to media. PGE2 synthesis, measured by radioimmunoassay, served as an index of prostaglandin H synthase activity. After a 24-hr incubation with 0.1 microM TPA or 1.0 microM A23187, arachidonic acid elicited significantly more PGE2 synthesis in agonist-treated cells than it did in control cells in primary culture. Microsomes from 24-hr TPA-treated cells exhibited significantly more prostaglandin H synthase activity than did those from control cells. In addition, the PGE2 content of overnight media was approximately 10-fold greater in TPA-treated cells than in control cells. The late (24 hr) response was more sensitive to lower concentrations of TPA than was the earlier (0-2 hr) response. TPA at 0.1 microM was a maximum effective dose for both responses. The 24-hr response was blocked by cycloheximide and staurosporine, inhibitors of protein synthesis and protein kinase C, respectively. Pretreatment of cells with aspirin, an irreversible inhibitor of prostaglandin H synthase, prior to addition of TPA did not prevent the late TPA-mediated increase in PGE2 synthesis. Subcultured cells exhibited both an early and a late TPA response. Only the early response was inhibited by aspirin pretreatment. Results suggest that the late response with TPA is caused by de novo synthesis of prostaglandin H synthase. Thus, primary and subcultured dog urothelial cells possess two distinct mechanisms for regulating signal transduction by arachidonic acid metabolism. This study provides a basis for assessing these mechanisms of signal transduction in urothelial cell lines and transformed cells.
authors.affiliation: VA Medical Center, St. Louis, Missouri.
authors.forename: T V
authors.initials: TV
authors.lastname: Zenser
authors.forename: D J
authors.initials: DJ
authors.lastname: Thomas
authors.forename: A K
authors.initials: AK
authors.lastname: Jacob
authors.forename: B B
authors.initials: BB
authors.lastname: Davis
mesh_terms: D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D001241:Aspirin / Q000494:pharmacology; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D015232:Dinoprostone / Q000096:biosynthesis; D004285:Dogs; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D001743:Urinary Bladder / Q000166:cytology / Q000201:enzymology*
chemical_list: D000470:Alkaloids; D016718:Arachidonic Acid; D003513:Cycloheximide; D011451:Prostaglandin-Endoperoxide Synthases; D019311:Staurosporine; D015232:Dinoprostone; D013755:Tetradecanoylphorbol Acetate; D001241:Aspirin