Control of endometrial phosphoinositide hydrolysis and prostaglandin F2alpha secretion in pigs

This study examined the control of endometrial phosphoinositide (PI) hydrolysis and prostaglandin (PG) F2alpha release by oxytocin (OT) and vasopressin in cyclic pigs on Day 15 post oestrus. In Expt 1, OT and arginine-vasopressin (AVP) increased endometrial PI hydrolysis (P<0.01), but only OT stimulated (P<0.01) PGF2alpha secretion. In Expt 2, OT and lysine-vasopressin (LVP) increased PI hydrolysis (P<0.01). No difference was detected between the 100 nM and 200 nM concentrations of OT or between the 100 nM and 200 nM concentrations of LVP. The increase in PI hydrolysis was greater (P<0.05) for 100 nM OT plus 100 nM LVP than for the 100 or 200 nM concentrations of OT or LVP alone. In Expt 3, OT (P<0.01) and LVP increased (P<0.01) PI hydrolysis. An OT antagonist abolished (P<0.01) the OT-induced increase in PI hydrolysis, but did not significantly alter the LVP-induced increase. A type 2 VP antagonist completely inhibited (P<0.01) the LVP-induced increase in PI hydrolysis, but only partially antagonized the stimulatory effect of OT (P<0.01). These results are consistent with the proposal that OT acts through specific receptors to promote endometrial PGF2alpha secretion in pigs.