[Phospholipase A2 activity in human cervical tissue at delivery].
Prostaglandins (PGs) play an important role in cervical ripening. It is known that the hydrolytic release of arachidonic acid from phospholipids regulates the rate of PG formation. To study the PG biosynthesis in cervical tissue, phosphatidylcholine containing 14C-arachidonic acid in Sn-2 position was incubated with the 800 X g supernatant of cervical tissue obtained from pregnant women at delivery. The only recognizable radiolabeled metabolite, 14C-arachidonic acid, was found on an autoradiogram of TLC, which corresponded to authentic arachidonic acid. Therefore, phospholipase A2 activity was calculated as the rate of the release of arachidonic acid from phosphatidylcholine under the conditions used. The optimal pH of phospholipase A2 activity in 800 X g supernatant was found to be 7.0. It was found that the addition of Ca2+ increased the enzyme activity. It was demonstrated that the concentrations of DHA-sulfate (DHA-S) and conjugated estrogens were higher in ripened cervical tissue than in non-ripened tissue and that PGI2 and PGE2 production increased following the addition of DHA-S. The effects of steroids mainly derived from feto-placental unit, cortisol, pregnenolone, 20 alpha-dihydroprogesterone, pregnenolone-sulfate, DHA, DHA-S, estrone, estradiol and estriol on arachidonic acid release were also studied in vitro. After the onset of labor. DHA-S was administered to the patients in vivo and their cervical tissues were collected at delivery. It was found that steroids including DHA-S did not affect phospholipase A2 activity under the conditions used. These results indicate that cervical tissue possesses the ability to release arachidonic acid from phospholipid, although this step in PG formation might not be affected by steroids including DHA-S.
D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D002584:Cervix Uteri / Q000187:drug effects / Q000201:enzymology*; D004492:Edetic Acid / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007743:Labor, Obstetric / Q000378:metabolism*; D010740:Phospholipases / Q000378:metabolism*; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D011247:Pregnancy; D011453:Prostaglandins / Q000378:metabolism
D001095:Arachidonic Acids; D004967:Estrogens; D011453:Prostaglandins; D016718:Arachidonic Acid; D004492:Edetic Acid; D010740:Phospholipases; D010741:Phospholipases A; D054467:Phospholipases A2; D002118:Calcium