Changes in Rat Uterine and Cervical Phospholipase A₂ Activity Following Progesterone Agonist or Antagonist Administration at Term

抄録

Our previous study revealed that a fall in plasma progesterone (P₄) level was associated with a transient increase in cytosolic phospholipase A₂ (PLA₂) activity and prostaglandin F₂α level in the rat uterus and cervix during natural parturition. This study determined the changes in the PLA₂ activities during modulated occurrence of delivery by P₄ antagonist or agonist late in pregnancy. In rats undergoing P₄ antagonist-induced preterm delivery, the PLA₂ activities of both uterine and cervical cytosol significantly decreased 12 h after the challenge and tended to be attenuated within 72 h. The plasma P₄ level altered in a similar pattern. Blockade of delivery by chronic treatment with P₄ agonist was not associated with changes in uterine PLA₂ activity compared with that in normally delivering rats, although there was a persistent rise in cervical PLA₂ activity. The obtained data indicates that the PLA₂ activities in rat uterine and cervical cytosol are not regulated solely by P₄ and that delivery can occur without activation of this enzyme.