Phospholipase a2 activity is increased in guinea pig uterine cervix
in late pregnancy and at parturition.
Rajabi, Mohammad R., and Andrey V. Cybulsky.
Departments of Obstetrics and Gynecology, and Biochemistry and
Molecular Biology, University of Medicine and Dentistry of New
Jersey, Newark, New Jersey 07103, and Department of Medicine, McGill
University, Montreal, Quebec, Canada H3A 1A1
APStracts 2:0130E, 1995.
Release of arachidonic acid from phospholipids by phospholipases A2
(PLA2) is the rate-limiting step in prostaglandin (PG) synthesis.
PGE2 and PGF2[alpha] are essential intermediates in interstitial
collagenase-mediated degradation of type I collagen, a key step in
cervical dilatation at parturition. We demonstrate that PLA2 is
present in cytosolic fractions of guinea pig cervix and PLA2 activity
is increased during cervical dilatation at parturition. In the cervix
of non-pregnant animals, PLA2 activity against phosphatidylcholine
(PLA2-PC) and phosphatidylethanolamine (PLA2-PE) was 13 +/- 6 and 49
+/- 27 pmol/min/mg protein, respectively. Levels were similar at day
25 of pregnancy. At day 50, PLA2-PC increased to 190 +/- 54
pmol/min/mg, and PLA2-PE rose to 592 +/- 127 pmol/min/mg. At
parturition (68 +/- 2 days), there were further increases of 49-67%.
PLA2 activity declined toward basal levels two days postpartum.
Almost 50% of the enhanced cytosolic PLA2 activity at day 50 or at
parturition was of high molecular mass, and was identified as the
"85kDa cPLA2". Increases in cPLA2 activity at these time
points were not, however, associated with increases in cPLA2 protein,
or phosphorylation of cPLA2, when compared to non-pregnant animals.
This study suggests that multiple PLA2 enzymes, including cPLA2, are
involved in cervical dilatation at parturition.
Received 22 March 1995; accepted in final form 6 June 1995.
APS Manuscript Number E135-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 July 1995.