title: Gestation age-related increase in 50-kDa rat uterine calcium-independent phospholipase A2 expression influences uterine sensitivity to polychlorinated biphenyl stimulation.
abstract: Phospholipase A2 (PLA2) enzymes catalyze the rate-limiting step in eicosanoid production by liberating arachidonic acid from membrane phospholipids. There is limited information regarding the expression pattern and activity of uterine PLA2 enzymes during pregnancy. Polychlorinated biphenyls (PCBs) are a group of persistent environmental toxicants previously associated with decreased gestation length that are capable of activating PLA2. The purpose of the present study was to determine whether uterine sensitivity to PCB stimulation is dependent on PLA2 expression, comparing rat uterine PLA2 expression in Gestational Day (gd) 10 versus gd20. Western blot analysis revealed a significant increase in the expression of calcium-dependent PLA2G2A and a 50-kDa protein immunoreactive to calcium-independent PLA2G6 antibody in gd20 compared to gd10 rat uterine tissue. The increased expression of the 50-kDa PLA2G6 was associated with a gestational age-related increase in endometrial calcium-independent PLA2 activity that was sensitive to inhibition by bromoenol lactone (P < 0.05). Longitudinal uterine strips isolated from gd10 or gd20 rat were suspended in muscle baths to evaluate uterine contractions following exposure to the ortho substituted congener PCB 50. Exposure to 50 and 100 microM PCB 50 significantly increased the frequency of gd20, but not gd10, uteri compared to solvent (dimethyl sulfoxide) controls (P < 0.05). Pharmacologic inhibition of PLA2G6, but not PLA2G2A, attenuated PCB-induced stimulation of gd20 uterine contractions (P < 0.05). These data suggest that PCB 50 stimulates uterine contractions by activating endometrial PLA2G6. Furthermore, gestation age-related sensitivity to PCB is associated with an increase in the expression of a previously unidentified 50-kDa PLA2G6 in rat uterus.
authors.affiliation: Department of Environmental Health Sciences, University of Michigan, Ann Arbor, Michigan 48109-2029, USA. kbrant@umich.edu
authors.forename: Kelly
authors.initials: K
authors.lastname: Brant
authors.forename: Wei
authors.initials: W
authors.lastname: Guan
authors.forename: Patricia
authors.initials: P
authors.lastname: Tithof
authors.forename: Rita Loch
authors.initials: RL
authors.lastname: Caruso
mesh_terms: D000818:Animals; D005260:Female; D005865:Gestational Age; D054522:Group VI Phospholipases A2; D066298:In Vitro Techniques; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054467:Phospholipases A2; D011078:Polychlorinated Biphenyls / Q000633:toxicity*; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D014590:Uterine Contraction / Q000187:drug effects*; D014599:Uterus / Q000187:drug effects / Q000201:enzymology*
chemical_list: D011078:Polychlorinated Biphenyls; D010741:Phospholipases A; D054522:Group VI Phospholipases A2; D054467:Phospholipases A2; C447028:2,2',4,6-tetrachlorobiphenyl