Late-gestation rat myometrial cells express multiple isoforms of phospholipase A2 that mediate PCB 50-induced release of arachidonic acid with coincident prostaglandin production.
Previous reports have shown that ortho-substituted polychlorinated biphenyls (PCBs) are uterotonic and activate phospholipase A2 to release arachidonic acid (AA) from membrane phospholipids. AA serves as the precursor to various eicosanoids, which, in addition to AA itself, are capable of modulating uterine function. To examine whether PCBs stimulate phospholipase A2 (PLA2) to mobilize arachidonic acid from late-gestation rat uterus, primary cultures of gestation day 20 (gd20) rat myometrial cells (RMC) were labeled with 0.5 microCi 3H-AA prior to a 10-, 20-, or 30-min exposure to 2,2',4,6-tetrachlorobiphenyl (PCB 50) (1-50 microM) or 0.1% DMSO (solvent control). PCB 50 stimulated the release of 3H-AA from gd20 RMC in concentration- and time-dependent manners (p < 0.05). PCB 50 stimulation of RMC was attenuated with ethylene glycol bis(2-aminoethyl ether)-N,N,N'N'-tetraacetic acid (EGTA) and nifedipine, suggesting that AA release was dependent on the influx of extracellular calcium through L-type voltage-operated calcium channels. PCB 50-induced release of AA from RMC was also attenuated with the PLA2-specific inhibitors methyl arachidonyl fluorophosphonate (MAFP), bromoenol lactone (BEL), and manoalide (p < 0.05). Stimulation of PLA2 enzymes in response to PCB exposure occurred via p38 mitogen activated protein kinase (MAPK) activation as indicated by the significant attenuation of PCB 50-induced AA release from RMC in the presence of SB 202190. In addition to stimulating AA release, PCB 50 induced a significant production of prostaglandins from gd20 RMC compared with controls (p < 0.05). These results suggest that myometrial cells express multiple PLA2 isoforms that may serve as a target and effector for ortho-substituted PCB-mediated stimulation of uterine function through arachidonic acid and prostaglandin release.
Brant
Kelly
K
Department of Environmental Health Sciences, University of Michigan, Ann Arbor, Michigan 48109-2029, USA. kbrant@umich.edu
Caruso
Rita Loch
RL
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000494:pharmacology; D004785:Environmental Pollutants / Q000633:toxicity*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005333:Fetus / Q000166:cytology; D007093:Imidazoles / Q000494:pharmacology; D009215:Myometrium / Q000187:drug effects / Q000196:embryology / Q000201:enzymology*; D009543:Nifedipine / Q000494:pharmacology; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054467:Phospholipases A2; D011078:Polychlorinated Biphenyls / Q000633:toxicity*; D011247:Pregnancy; D011453:Prostaglandins / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013047:Specific Pathogen-Free Organisms
D020746:Calcium Channels, L-Type; D002614:Chelating Agents; D004785:Environmental Pollutants; D004791:Enzyme Inhibitors; D007093:Imidazoles; D011453:Prostaglandins; D011725:Pyridines; D016718:Arachidonic Acid; D004533:Egtazic Acid; D011078:Polychlorinated Biphenyls; D010741:Phospholipases A; D054467:Phospholipases A2; D009543:Nifedipine; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole