EFFECT OF OXYTOCIN ON CONCENTRATIONS OF PROSTAGLANDIN-H SYNTHASE-2 MESSENGER-RNA IN-OVINE ENDOMETRIAL TISSUE IN-VIVO

Oxytocin is an acute stimulus of prostaglandin (PG) F-2 alpha secretio n from the ovine uterine endometrium. The high level of PGF(2 alpha) s ecretion induced by oxytocin and the short half-life of the prostaglan din synthase-2 (PGHS-2) enzyme implies that synthesis of PGHS-2 may be essential at this time. The objective of this study was to determine if the increase in PGF(2 alpha) secretion induced by oxytocin is assoc iated with an increase in PGHS-2 mRNA. In experiment 1, oxytocin induc ed a rapid increase in serum concentration of 13,14-dihydro-15-keto-pr ostaglandin F-2 alpha (the stable metabolite of PGF(2 alpha); PGFM) th at was detected within 7.5 min (P < 0.05) and peaked at 25 min post in jection, This was associated with an unusually rapid increase in the c oncentration of PGHS-2 mRNA at 25 min post oxytocin injection (P < 0.0 5). Endometrial concentrations of PGHS-2 mRNA returned to basal levels at 90 min post injection. Experiment 2 was conducted to further chara cterize the time course of induction of PGHS-2 mRNA following oxytocin administration. Oxytocin induced a rapid increase in serum concentrat ions of PGFM. As in experiment 1, an increase in concentrations of PGH S-2 mRNA was detected at 25 min after oxytocin (P = 0.06). Concentrati ons of PGHS-2 mRNA were intermediate at 40 min and returned to basal l evels at 60 min post injection. Thus, there is a rapid increase in end ometrial concentrations of PGHS-2 mRNA following oxytocin stimulation of PGF(2 alpha), secretion. This increase in PGHS-2 mRNA may be requir ed to maintain PGHS-2 enzyme levels during pulsatile secretion of PGF( 2 alpha) at luteolysis.