In Vitro Secretion of Prostaglandins from Endometrium of Postpartum Beef Cows Expected to have Short or Normal Luteal Phases1

Abstract

The objective of this study was to characterize endometrial secretion (in vitro) of prostaglandin F (PGF), 15-keto-13,14-dihydro-prostaglandin F2 alpha (PGFM), prostaglandin E2 (PGE2), and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) on Day 5 following the first postpartum estrus of cows anticipated to have a short compared to a normal estrous cycle. Twenty-seven beef cows were randomly assigned into four groups. The Short Cycle (n = 6; control) and Short Cycle/Explant (n = 8; endometrial explants) groups had their calves weaned at 30-32 days postpartum. The Normal Cycle (n = 5, control) and Normal Cycle/Explant (n = 8; endometrial explants) groups received norgestomet (progestin) implants for 9 days beginning 21-23 days postpartum, and calves were weaned at implant insertion. Estrous cycle length (mean +/- SE; p less than 0.01) for the Short Cycle group was 11.5 +/- 1.9 days compared to 18.8 +/- 0.6 days for the Normal Cycle group. On Day 5 following the first postpartum estrus, cows in the Short Cycle/Explant and Normal Cycle/Explant groups were hysterectomized, and endometrial explants were incubated in Earle's Balanced Salt solution/Medium 199 for 90 min with or without arachidonic acid (AA) in the presence of three levels of oxytocin. Mean concentrations of PGF and PGFM were combined to obtain a value for total PGF. Concentrations of total PGF, PGE2 (from explants without AA treatment), and 6-keto-PGF1 alpha in medium of the Short Cycle/Explant group were higher (p less than 0.01) than in medium of the Normal Cycle/Explant group.(ABSTRACT TRUNCATED AT 250 WORDS)

Luteal function after intrauterine infusion of recombinant bovine interferon- I1 into postpartum beef cows expected to have short or normal luteal phases

“…Secretion of progesterone was similar to that observed in cows during a normal oestrous cycle (Copelin et al, 1987(Copelin et al, , 1989. In other studies, pulse amplitude and basal concentrations of plasma PGF2a were increased on days 4-9 for postpartum cows having a short rather than a normal length oestrous cycle (Cooper et al, 1991), and secretion of PGF2a in vitro from endometrial tissue from cows anticipated to have short (Zollers et al, 1991b). Injection of oxytocin on day 5 of the oestrous cycle induced a release of 13,14-dihydro-15-keto prostaglandin F2a (PGFM) in cows with a short, but not normal, oestrous cycle length (Zollers et al, 1989).…”

Maintenance or regression of the corpus luteum during multiple decisive periods of bovinepregnancy

“…Active immunization against PGF (Copelin et al, 1989) or inhibition of PGF secretion were both effective in extending the CL lifespan and increasing P4 secretion by the CL, indicating that uterine PGF is the primary cause of the shortened luteal phase. Consistent with this idea, cows destined to have short-lived CL have early secretion of PGF from the uterus (Zollers et al, 1991) and an early increase in circulating metabolite of PGF that begins near the time of the first increases in circulating E2 during the first follicular wave (Southee et al, 1988;Hunter et al, 1989;Cooper et al, 1991;Hunter, 1991;Garverick et al, 1992b). In addition, intrauterine infusion of IFNT, the protein that normally causes maintenance of the CL during pregnancy in ruminants, can prevent short luteal phases (Garverick et al, 1992a).…”

Luteal Function: The Estrous Cycle and Early Pregnancy

“…This short luteal phase has been studied extensively in beef cattle; it occurs at puberty [92] and during the transition from postpartum anestrus to cyclicity [93]. Evidence is accumulating that the CL regresses early as a result of a premature release of PGF 2 a from the uterus [94].…”