TY - JOUR
T1 - Delayed effect of low progesterone concentrations on bovine uterine PGF2α secretion in the subsequent oestrous cycle
AU - Shaham-Albalancy, A.
AU - Folman, Y.
AU - Kaim, M.
AU - Rosenberg, M.
AU - Wolfenson, D.
PY - 2001
Y1 - 2001
N2 - Low progesterone concentrations during the bovine oestrous cycle induce enhanced responsiveness to oxytocin challenge late in the luteal phase of the same cycle. The delayed effect of low progesterone concentrations during one oestrous cycle on uterine PGF2α secretion after oxytocin challenge on day 15 or 16 of the subsequent cycle was studied by measuring the concentrations of the major PGF2α metabolite (13,14-dihydro-15-keto PGF2α; PGFM) in plasma. Two experiments were conducted, differing in the type of progesterone treatment and in the shape of the low progesterone concentration curves. In Expt 1, progesterone supplementation with intravaginal progesterone inserts, with or without an active corpus luteum, was used to obtain high, or low and constant plasma progesterone concentrations, respectively. In Expt 2, untreated cows, representing high progesterone treatment, were compared with cows that had low but increasing plasma progesterone concentrations that were achieved by manipulating endogenous progesterone secretion of the corpus luteum. Neither experiment revealed any differences in plasma progesterone concentrations between the high and low progesterone groups in the subsequent oestrous cycle. In both experiments, both groups had similar basal concentrations of PGFM on day 15 (Expt 1) or 16 (Expt 2) of the subsequent oestrous cycle, 18 days after progesterone treatments had ended. In both experiments, the increases in PGFM concentrations in the low progesterone groups after an oxytocin challenge were markedly higher than in the high progesterone groups. These results indicate that low progesterone concentrations during an oestrous cycle have a delayed stimulatory effect on uterine responsiveness to oxytocin during the late luteal phase of the subsequent cycle. This resulting increase in PGF2α secretion may interfere with luteal maintenance during the early stages of pregnancy.
AB - Low progesterone concentrations during the bovine oestrous cycle induce enhanced responsiveness to oxytocin challenge late in the luteal phase of the same cycle. The delayed effect of low progesterone concentrations during one oestrous cycle on uterine PGF2α secretion after oxytocin challenge on day 15 or 16 of the subsequent cycle was studied by measuring the concentrations of the major PGF2α metabolite (13,14-dihydro-15-keto PGF2α; PGFM) in plasma. Two experiments were conducted, differing in the type of progesterone treatment and in the shape of the low progesterone concentration curves. In Expt 1, progesterone supplementation with intravaginal progesterone inserts, with or without an active corpus luteum, was used to obtain high, or low and constant plasma progesterone concentrations, respectively. In Expt 2, untreated cows, representing high progesterone treatment, were compared with cows that had low but increasing plasma progesterone concentrations that were achieved by manipulating endogenous progesterone secretion of the corpus luteum. Neither experiment revealed any differences in plasma progesterone concentrations between the high and low progesterone groups in the subsequent oestrous cycle. In both experiments, both groups had similar basal concentrations of PGFM on day 15 (Expt 1) or 16 (Expt 2) of the subsequent oestrous cycle, 18 days after progesterone treatments had ended. In both experiments, the increases in PGFM concentrations in the low progesterone groups after an oxytocin challenge were markedly higher than in the high progesterone groups. These results indicate that low progesterone concentrations during an oestrous cycle have a delayed stimulatory effect on uterine responsiveness to oxytocin during the late luteal phase of the subsequent cycle. This resulting increase in PGF2α secretion may interfere with luteal maintenance during the early stages of pregnancy.
UR - http://www.scopus.com/inward/record.url?scp=0034779868&partnerID=8YFLogxK
U2 - 10.1530/rep.0.1220643
DO - 10.1530/rep.0.1220643
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C2 - 11570971
AN - SCOPUS:0034779868
SN - 1470-1626
VL - 122
SP - 643
EP - 648
JO - Reproduction
JF - Reproduction
IS - 4
ER -