title: Lipocortin-independent effect of dexamethasone on phospholipase activity in a thymic epithelial cell line.
abstract: In the cloned rat thymic endocrine epithelial cell line TEA3A1, treatment with dexamethasone leads to decreased levels of prostaglandin E2, prostaglandin F2 alpha, and thromboxane B2. Dexamethasone treatment also leads to a decrease of both calcium-dependent and calcium-independent phospholipase A2 activity measured in a cell-free assay. Dexamethasone-treated cells also have increased levels of lipocortin-I, a putative modulator of phospholipase A2 activity. The property of calcium-dependent binding of lipocortin to the particulate fraction was used to prepare cytosolic and particulate subcellular fractions which contained phospholiphase A2 activity but no lipocortin-I. Dexamethasone decreased phospholipase A2 activity in both cytosolic and particulate fractions even in the absence of lipocortin, suggesting the presence of a lipocortin-independent mechanism.
authors.affiliation: W. Alton Jones Cell Science Center, Inc., Lake Placid, NY 12946.
authors.forename: A
authors.initials: A
authors.lastname: Piltch
authors.forename: L
authors.initials: L
authors.lastname: Sun
authors.forename: R A
authors.initials: RA
authors.lastname: Fava
authors.forename: J
authors.initials: J
authors.lastname: Hayashi
mesh_terms: D000818:Animals; D017302:Annexins; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002460:Cell Line; D003907:Dexamethasone / Q000494:pharmacology*; D004848:Epithelium / Q000187:drug effects / Q000201:enzymology; D010740:Phospholipases / Q000037:antagonists & inhibitors*; D010741:Phospholipases A / Q000037:antagonists & inhibitors*; D054467:Phospholipases A2; D051381:Rats; D013950:Thymus Gland / Q000187:drug effects / Q000201:enzymology*
chemical_list: D017302:Annexins; D002135:Calcium-Binding Proteins; D003907:Dexamethasone; D010740:Phospholipases; D010741:Phospholipases A; D054467:Phospholipases A2