Visiting Fulbright scholar at Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA.
Endometrial Phospholipase A2 Activity During the Oestrous Cycle and Early Pregnancy in Mares
Article first published online: 7 APR 2012
© 2012 Blackwell Verlag GmbH
Reproduction in Domestic Animals
Volume 48, Issue 1, pages 46–52, February 2013
How to Cite
Ababneh, M. and Troedsson, M. (2013), Endometrial Phospholipase A2 Activity During the Oestrous Cycle and Early Pregnancy in Mares. Reproduction in Domestic Animals, 48: 46–52. doi: 10.1111/j.1439-0531.2012.02023.x
- Issue published online: 15 JAN 2013
- Article first published online: 7 APR 2012
- Submitted: 4 Jan 2012; Accepted: 8 Mar 2012
The aim of this study was to determine phospholipase A2 (PLA2) kinetics and activity in the mare’s endometrium during the oestrous cycle and early pregnancy. Phospholipase A2 is responsible for the liberation of arachidonic acid from phospholipids, which is the first limiting step in prostaglandins synthesis. Phospholipase A2 activity was measured using an assay based on the liberation of oleic acid from 1-palmitoyl-2-[14C] oleoyl phosphatidylcholine. The enzyme was shown to be calcium dependent, to have an optimum pH of 8 and an apparent Michaelis constant of 127 μm. Enzyme activity was low in the endometrium of early luteal phase tissue but increased significantly (p < 0.001) during the late luteal phase (5.39 ± 0.16; 3.48 ± 0.33, 6.85 ± 0.59, and 9.96 thinsp;± thinsp;1.23 thinsp;nmol oleic acid released/mg protein at oestrus, and Days 3, 8 and 14 after ovulation, respectively). The mean PLA2 activity in endometrial tissue from pregnant mares (4.23 ± 0.74) was significantly lower (p < 0.01) than from cyclic animals during late dioestrus (9.96 ± 1.23). The results indicate that PLA2 activity in equine endometrium changes with the stage of the oestrous cycle and thus may be influenced by systemic hormone concentrations. The inhibitory effects of conceptus products on secretion of prostaglandin during early pregnancy were associated with a competitive inhibitor that decreased endometrial PLA2 activity.