Secretory type II PLA(2) immunoreactivity and PLA(2) enzymatic activity inhuman gestational tissues before, during and after spontaneous-onset labour at term

Arachidonic acid mobilization by phospholipase A(2) (PLA(2)) and subsequent prostaglandin synthesis is thought to be a pivotal event in the onset and/ or maintenance of human labour. The purpose of this study was to quantify s ecretory PLA(2) (sPLA(2)) and non-secretory PLA(2) enzymatic activity and t ype II sPLA(2) immunoreactivity in human gestational tissues before, during and after labour of spontaneous onset. Placental tissue and fetal membrane s were collected from women before, during and after spontaneous-onset labo ur at term and stored at - 80 degrees C. PLA(2) activity in supernatants wa s quantified by radiolabelled substrate assay (C-14-phosphatidylethanolamin e) with and without 12.5 mM dithiothreitol (DTT) to separate enzymatic acti vity contributed by secretory and non-secretory PLA(2) components. Immunore active type II PLA(2) in supernatants was determined by a monoclonal, non-c ompetitive sandwich ELISA. Total PLA(2) enzymatic activity in amnion, chori odecidua and placenta was not significantly different before, during and af ter labour (n=18-20). Likewise, non-secretory enzymatic activity was not si gnificantly different before (n = 9), during (n = 10) and after labour (n = 9) in any of the three types of gestational tissue examined. Although immu noreactive type II PLA(2) was significantly higher in the placenta (P<0.01) compared to amnion and choriodecidua, there was no significant difference in immunoreactive type II PLA(2) within each tissue group according to labo ur status (n=18-20). Overall, no change in PLA(2) secretory or non-secretor y enzymatic activity or immunoreactive type II PLA(2) could be detected thr oughout the peripartum period. (C) 1999 W. B. Saunders Company Ltd.