Submission Number: GRE-4-99-113
Abstract Number: 398
INTERESTROUS INTERVAL OF CYCLIC GILTS IS DECREASED BY SYSTEMIC BUT NOT INTRAUTERINE ADMINISTRATION OF EXOGENOUS OXYTOCIN.
GL Sample 1,2, SL Kubotsu* 1, Kevin G Carnahan 1, DM Blackwell* 1 and MA Mirando* 1
Department of Animal Sciences, Washington State Univ, Pullman, WA 1
College of Veterinary Medicine, Washington State Univ, Pullman, WA 2
Oxytocin (OT) stimulates uterine release of prostaglandin F2 (PGF2) in pigs, but the role of OT in control of luteolysis during the estrous cycle and early pregnancy is not clear. We hypothesize that systemic OT is luteolytic, but that endometrial OT is antiluteolytic. These studies determined if OT, administered either systemically or into the uterine lumen, altered 13,14-dihydro-15-keto-PGF2 (PGFM) concentrations (Exp 1) or interestrous interval (IEI; Exp 2-4) of cyclic gilts. In Exp 1, intrauterine infusion of 80 USP units OT on days 10, 12, 14 and 16 postestrus attenuated the increase in PGFM 30% on day 14 (P<0.09) and 62% on day 16 (P<0.01) compared with controls (treatment day interaction, P<0.01). In Exp 2, intrauterine infusion of 80 USP units 3/day on days 10-16 did not decrease IEI (24.5 1.3 d) compared to controls (22.5 1.3 d). In contrast, i.m. injections of 20 USP units OT 2/day or 80 USP units OT 3/day on days 10-16 in Exp 3 decreased (P<0.05) IEI (20.0 0.3 or 19.5 0.4 d, respectively) compared to controls (20.5 0.3 d). When gilts received a single i.m. injection of 0 or 1 mg of estradiol valerate on day 11 and i.m. injections of 0 or 20 USP units OT 3/day on days 10-16 in Exp 4, OT decreased IEI in the absence of estradiol (19.0 0.5 d) compared with injection of vehicle (20.4 0.5 d). In gilts receiving 1 mg of estradiol valerate to inhibit luteolysis, OT did not prevent the increase in IEI (25.4 0.5 d) compared with injections of vehicle (24.7 0.5 d) (OT estradiol interaction, P=0.05). These results indicate that: 1) intrauterine infusion of OT on days 10-16 attenuated the increase in PGFM and was not luteolytic; 2) OT administered i.m. on days 10-16 shortened IEI, and 3) OT did not prevent the increase in IEI induced by estradiol valerate. These results are consistent with the hypothesis that systemically-derived OT is luteolytic, but endometrially-derived OT has an antiluteolytic effect to suppress endocrine secretion of PGF2. This work was supported by a Summer Research Fellowship from the College of Veterinary Medicine.
Keywords: Uterus, oviduct
This abstract is being presented at: 8:00 AM in session: