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Pregnancy Induces Expression of cPLA2 in Ovine Uterine Artery but Not Systemic Artery Endothelium

Jeremy A. Sullivan, BS

Heidi L. Rupnow, BS

Ronald R. Magness, PhD

Department of Obstetrics and Gynecology, Perinatal Research Laboratories and Department of Animal Sciences, University of Wisconsin-Madison, Madison, Wisconsin

Ian M. Bird, PhD

Department of Obstetrics and Gynecology, Perinatal Research Laboratories and Department of Animal Sciences, University of Wisconsin-Madison, Madison, Wisconsin; imbird{at}facstaff.wise.edu

Objective: To determine whether pregnancy increases cytosolic phospholipase A₂ (cPLA₂) expression in uterine artery (UA) endothelial cells and vascular smooth-muscle (VSM) cells, and whether ovarian steroid mediate this effect.

Methods: Uterine arteries and omnetal arteries (systemic control) were isolated from pregnant (120-130 days' gestation) ewes and from nonpregnant ewes synchronized to the corresponding phases of the ovarian cycle (follicular or luteal) or ovariectomized. In addition, ovariectomized ewes were treated with vehicle, estradiol-17ß (E2ß), progesterone (P4), or combined E2ß/P4 for 10 days, and UAs were collected. Arteries from all studies were separated into mechanically isolated endothelial and VSM fractions. Proteins were then solubilized and separated on 7.5% sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by Western immunoblotting using an affinity-purified mouse monoclonal antibody for cPLA₂.

Results: Both UA endothelium and VSM fractions were seen to express cPLA₂, detected as a single band with a molecuular mass similar to that observed in myometrium (about 100 kD). Distribution of cPLA₂, when expressed per microgram of protein, was observed as 40% in UA endothelium compared with 60% in VSM fractions. Uterine artery endothelial cPLA₂ expression was specifically increased 1.9-fold in pregnancy (P < .05), whereas there was no significant change from VSM. Furthermore, in variectomized sheep versus intact luteal or follicular phase animals, there was no significant change in cPLA₂ expression in endothelium or VSM. Administration of E2ß, P4, or their combination in ovariectomized sheep also failed to reproduce the pregnancy-induced increase in cPLA₂ expression in UA endothelium. Omental artery endothelial and VSM cPLA₂ expression was observed at similar magnitudes as UA expression, but levels were consistently unchanged by pregnancy, the ovarian cycle, or ovariectomy.

Conclusions: cPLA₂ was expressed throughout the endothelium and VSM of both uterine and omental arteries, but only in UA endothelium was pregnancy associated with elevated cPLA₂ expression. The lack of change in cPLA₂ expression with the ovarian cycle or in ovariectomized animals, even after prolonged treatment with E2ß, P4, or E2ß/P4 combined suggests this pregnancy-induced increase in cPLA₂ may not be estrogen and/or progesterone dependent.

Key Words: Cytosolic phospholipase A2 • pregnancy • uterine artery • endothelium

Journal of the Society for Gynecologic Investigation, Vol. 6, No. 6, 301-306 (1999)
DOI: 10.1177/107155769900600604


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