Regulation of prostaglandin synthesis by thyrotropin, insulin or insulin-like growth factor-I, and serum in FRTL-5 rat thyroid cells.
The present report shows that thyrotropin (TSH) regulates all three steps involved in prostaglandin synthesis in FRTL-5 rat thyroid cells, i.e. arachidonic acid release from membrane phospholipids, cyclooxygenase (prostaglandin H synthase) action, and individual prostaglandin formation; however, its action at specific steps may require the presence of, or can be duplicated by, insulin, insulin-like growth factor-I (IGF-I), and/or a serum factor. Thus, TSH releases free arachidonic acid from rat FRTL-5 thyroid cells whose phospholipid fraction is radiolabeled with [3H]arachidonic acid; this action involves a pertussis toxin-sensitive G protein, is not cAMP mediated, and does not require insulin or 5% serum. To quantitate TSH effects on cyclooxygenase activity and on individual prostaglandin formation, a homogenate system and a rapid reversed-phase high pressure liquid chromatography procedure have been developed to measure cyclooxygenase metabolites. TSH increased cyclooxygenase activity in homogenates only if the cells were also exposed to insulin, IGF-I, and/or 5% calf serum; TSH alone had no apparent effect on the activity. Maximal activation, 4-fold over basal/micrograms of DNA, took 36 h to achieve and reflected, at least in part, an increase in cyclooxygenase gene expression. Like cyclooxygenase activity, induction of prostaglandin E2 production required 2 or more factors, i.e. TSH plus insulin/IGF-I or TSH plus insulin/IGF-I plus serum. Increased production of prostaglandin D2, could, however, be detected if cells were treated with TSH alone and the TSH activity could be duplicated by insulin, IGF-I, or calf serum alone.
Tahara
K
K
Section of Cell Regulation, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892.
Grollman
E F
EF
Saji
M
M
Kohn
L D
LD
D015117:5,8,11,14-Eicosatetraynoic Acid / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D003470:Culture Media; D000242:Cyclic AMP / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000302:isolation & purification / Q000378:metabolism; D007213:Indomethacin / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007700:Kinetics; D009637:Masoprocol / Q000494:pharmacology; D008954:Models, Biological; D010743:Phospholipids / Q000378:metabolism; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D011453:Prostaglandins / Q000096:biosynthesis* / Q000302:isolation & purification; D051381:Rats; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology*
D001095:Arachidonic Acids; D003470:Culture Media; D005231:Fatty Acids, Unsaturated; D007328:Insulin; D010743:Phospholipids; D011453:Prostaglandins; D015117:5,8,11,14-Eicosatetraynoic Acid; D016718:Arachidonic Acid; D007334:Insulin-Like Growth Factor I; D009637:Masoprocol; D013972:Thyrotropin; D000242:Cyclic AMP; D011451:Prostaglandin-Endoperoxide Synthases; D007213:Indomethacin