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1 October 2001 Cellular Mechanisms by Which Oxytocin Mediates Ovine Endometrial Prostaglandin F Synthesis: Role of Gi Proteins and Mitogen-Activated Protein Kinases
Patrick D. Burns, Jose´ O. B. Mendes, Jr., Robert S. Yemm, Colin M. Clay, Scott E. Nelson, Susan H. Hayes, William J. Silvia
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Abstract

Oxytocin stimulates a rapid increase in ovine endometrial prostaglandin (PG) F synthesis. The overall objective of these experiments was to investigate the cellular mechanisms by which oxytocin induces endometrial PGF synthesis. The objective of experiment 1 was to determine whether Gi proteins mediate oxytocin-induced PGF synthesis. Uteri were collected from four ovary-intact ewes on Day 14 postestrus. Caruncular endometrial explants were dissected and subjected to in vitro incubation. Pertussis toxin, an inhibitor of Gi proteins, had no effect on the ability of oxytocin to induce PGF synthesis (P > 0.10). The objective of experiment 2 was to determine whether any of the three mitogen-activated protein kinases (MAPKs), extracellular signal regulated protein kinase (ERK1/2), c-Jun N-terminal/stress-activated protein kinase (JNK/SAPK), or p38 MAPK, mediate oxytocin-induced PGF synthesis. Eleven ovary-intact ewes were given an injection of oxytocin (10 IU; i.v.; n = 5) or physiological saline (i.v.; n = 6) on Day 15 postestrus. Uteri were collected 15 min after injection and caruncular endometrium was dissected. Endometrial homogenates were prepared and subjected to Western blotting. Membranes were probed for both total and phosphorylated forms of all three classes of MAPK. All classes of MAPK were detected in ovine endometrium, but oxytocin treatment had no effect on the expression of these proteins (P > 0.10). ERK1/2 was the only phosphorylated MAPK detected and its concentrations were higher in oxytocin-treated ewes (P < 0.01). The objective of experiment 3 was to further investigate the role of ERK1/2 during oxytocin-induced PGF synthesis. Uteri were collected from four ovary-intact ewes on Day 14 postestrus. Caruncular endometrial explants were dissected and subjected to in vitro incubation. PD98059, a specific inhibitor of ERK1/2 activity, blocked the ability of oxytocin to stimulate PGF synthesis in a dose-dependent manner (P < 0.05). These results indicate that the ovine oxytocin receptor is not coupled to Gi proteins. These results indicate that oxytocin induces phosphorylation of ERK1/2 and that this MAPK appears to mediate oxytocin-induced PGF synthesis in ovine endometrium.

Patrick D. Burns, Jose´ O. B. Mendes, Jr., Robert S. Yemm, Colin M. Clay, Scott E. Nelson, Susan H. Hayes, and William J. Silvia "Cellular Mechanisms by Which Oxytocin Mediates Ovine Endometrial Prostaglandin F Synthesis: Role of Gi Proteins and Mitogen-Activated Protein Kinases," Biology of Reproduction 65(4), 1150-1155, (1 October 2001). https://doi.org/10.1095/biolreprod65.4.1150
Published: 1 October 2001
JOURNAL ARTICLE
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KEYWORDS
kinases
mechanisms of hormone action
oxytocin
signal transduction
uterus
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