PARENT SESSION
Pregnancy and Parturition

EFFECT OF STEROIDS, OXYTOCIN AND PREGNANCY ON PROSTAGLANDIN F₂ SECRETION BY STROMAL AND POLARIZED LUMINAL EPITHELIAL CELLS FROM PIG ENDOMETRIUM.

Assiri, Abdullah¹, Hu, Jianbo¹, Ott, Troy², Mirando, Mark¹, ^{1 2}

ABSTRACT- During early pregnancy in pigs, luteolysis is blocked by a conceptus estrogen-induced redirection of prostaglandin F₂ (PGF₂) secretion toward the uterine lumen. To examine the effect of estrogen (E₂), progesterone (P₄) and oxytocin (OT) on endometrial PGF₂ release, luminal epithelial (LEC) and stromal cells (SC) from 7 cyclic and 7 pregnant gilts were isolated 16 days post-estrus and cultured in steroid-free medium or media containing 10 nM E₂ , 100 nM P₄ , or 10 nM E₂ + 100 nM P₄. LEC were grown on 12-mm Millicell-HA inserts until confluent and polarized, then treated on the apical and basal surfaces with 0 or 100 nM OT for 3 hr. SC were seeded in 24-well plates and treated with 0 or 100 nM OT for 3 hr. PGF₂ secretion from the basal surface of LEC was greater (p<0.01) than from the apical surface in both cyclic and pregnant gilts. Basal PGF₂ secretion was greater (p=0.01) from LEC of cyclic than pregnant gilts. Secretion of PGF₂ from the basal surface was increased (p<0.01) by E₂ , P₄ , and E₂ + P₄ in both cyclic and pregnant gilts. OT stimulated (p<0.01) PGF₂ secretion in SC from both cyclic and pregnant gilts. However, P₄ reduced (p<0.05) OT-induced PGF₂ secretion in cyclic and pregnant gilts and E₂ + P₄ further decreased (p<0.01) the response to OT in SC from pregnant gilts. These results suggest that PGF₂ release from the basal surface of LEC and induced from SC by OT may be important in luteolysis. Redirection of PGF₂ secretion away from the uterine vasculature during pregnancy recognition is most attributable to reduced PGF₂ release from the basal surface of LEC and decreased response to OT of SC exposed to conceptus E₂ in the presence of P₄ . This research was supported by NIH grant HD 30268.

KEY WORDS: Endometrium(pig), PGF ₂ , Directional, Steroids