Date of Award

Spring 1998

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemistry & Biochemistry

Program/Concentration

Chemistry

Committee Director

Miriam D. Rosenthal

Committee Member

Patricia A. Pleban

Committee Member

Mark S. Elliott

Call Number for Print

Special Collections LD4331.C45 D86

Abstract

Cytosolic phospholipase A2 ( cPLA2) specifically catalyzes the release of arachidonate from membrane phospholipids, thus initiating synthesis of prostaglandins, thromboxanes, and other eicosanoids. The human and nonhuman primate placenta actively synthesize high levels of eicosanoids which play both an autocrine and paracrine role in placental function. Previous studies in Dr. Miriam D. Rosenthal's laboratory have shown that cPLA2 mRNA levels are developmentally regulated. The present study was designed to determine whether placental cPLA2 protein levels increased during gestation. Since the marked increases in estrogen levels during normal pregnancy have been shown to enhance morphological and biochemical differentiation of the placenta, we also sought to determine whether expression of cPLA2 protein was affected by estrogen. The first experiment examined placental samples from different stages of normal pregnancy. Pieces of whole villous tissue (four placentas per time point) were obtained at early (day 60), mid (day 100), and late (day 165) gestation (term= 184 days) and homogenized in sample buffer containing protease inhibitors. Aliquots (40 μg/lane) were separated by SDS-PAGE on 8% polyacrylamide gels and electroblotted onto Immobilon-P membranes. A specific monoclonal antibody against mouse cPLA2 was used and the protein bands were visualized by enhanced chemilumenescence. As expected from studies with other human and rodent tissues, the antibody detected an 85 kDa protein in baboon placental samples. Densitometric analysis indicated a significant increase in cPLA2 between early and late gestation (0.6 ± 0.14 vs. 2.5 ± 0.68 arbitrary units, p < 0.02). In order to investigate the effects of estrogen, samples were obtained from late gestation baboons which had been treated during days 140-165 with an aromatase inhibitor (AI). Inhibition of estrogen synthesis decreased placental cPLA2 protein levels by approximately fifty- percent. Placentas from AI-treated animals in which maternal serum estradiol levels had been partially restored by treatment with estradiol had cPLA2 levels similar to AI treated animals rather than controls. By contrast, maternal estradiol treatment actually decreased cPLA2 levels in early (day 60) placentas (2.94 ± 0.49 vs. 1.61 ± 0.75 arbitrary units, p < 0.02). These results indicate that levels of cPLA2 protein in whole villous placenta increase during gestation. Furthermore, increased expression of placental cPLA2 protein in late pregnancy appears to require the normal increases in serum estrogen levels.

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DOI

10.25777/2dvt-3s57

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