Increase in prostaglandin H synthase 2, but not prostaglandin F-2 alpha synthase mRNA in intrauterine tissues during betamethasone-induced premature labor and spontaneous term labor in sheep

OBJECTIVE: Prostaglandin F synthase (PGFS) catalyzes reduction of prostagla ndin H-2 to PGF(2 alpha). No information exists on PGFS expression and regu lation during pregnancy, either mRNA or protein, in relation to labor in ut erine tissues in any species. We characterized PGFS mRNA expression in ovin e myometrium, endometrium, maternal and fetal placenta in betamethasone-ind uced premature labor and spontaneous term labor using our cloned ovine PGFS riboprobe. Prostaglandin H synthase (PGHS) 2 mRNA was evaluated simultaneo usly as a control whose pregnancy related changes are well known. METHODS: Poly-A or total RNA from fetal placenta, myometrium, and endometri um in control ewes at 143-147 days of gestational age (dGA, TCNL, n = 6), a nd ewes in spontaneous term labor at 145-147 dGA (STL, n = 6) and endometri um and maternal and fetal placenta in early control ewes not in labor (ECNL , n = 6) and betamethasone induced labor at 128-135 dGA (BL, n = 6) were an alyzed for PGHS2 and PGFS mRNA. RESULTS: PGFS mRNA did not change at spontaneous term labor in myometrium, endometrium, and fetal placenta. PGFS mRNA decreased during betamethasone-i nduced premature labor in endometrium and maternal placenta (P < .05), but remained unchanged in fetal placenta and myometrium. PGHS2 mRNA increased i n endometrium, placenta, and myometrium during betamethasone-induced premat ure labor and spontaneous term labor. CONCLUSION: Increased PGHS2, but not PGFS mRNA was tightly associated with the onset of betamethasone-induced premature labor as well as spontaneous t erm labor in the endometrium, placenta, and myometrium. Transcription of PG FS mRNA may not be the rate-limiting step in the pathway contributing to in creased PGF(2 alpha) at labor. Copyright (C) 2001 by the Society for Gyneco logic Investigation.