Acute actions of prostaglandin F(2α), E2, and I2 in microdialyzed bovine corpus luteum in vitro

A. Miyamoto, H. V. Lutzow, D. Schams

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76 Scopus citations

Abstract

The bovine CL is one of the sites for the production of prostaglandins (PG). Although many in vitro models, mainly using dispersed luteal cell incubations, have shown the variety of CL responses to PGs (luteotropic, no effect, or luteolytic), the functional role of luteal PGs in cattle remains to be elucidated. Therefore, the aim of the present study was to examine the effects of PGs with respect to progesterone (P4) and oxytocin (OT) release from the bovine CL in vitro (Days 8-12 of the estrous cycle) via a microdialysis system (MDS), in which intact cell-to-cell contact exists. Thirty-minute perfusion with PGF(2α), PGE2, and PGI2 (10-10-10-5 M) induced significant, but different, acute effects. PGF(2α) and PGE2 clearly stimulated hormone (P4 and OT) release, while PGI2 slightly inhibited hormone secretion during infusion at low doses but stimulated secretion at 10-6 and 10-5 M concentrations. Additionally, catabolized PGF(2α) and PGI2 (13,14-dihydro-15-keto-PGF(2α) [PGFM] and 6-keto-PGF(1α), respectively) induced responses different from those of the original PGs; both PGFM and 6-keto-PGF(1α) at low doses weakly inhibited P4 release, but at 10-5 M concentration stimulated release. Phorbol 12-myristate 13- acetate (TPA), a potent stimulator of the protein kinase C (PKC) system in bovine luteal cells, stimulated P4 and OT release when administered alone. Pre-exposure with TPA (10-9 M) for 2.5 h resulted in an increase in the stimulative potency of PGF(2α) and PGI2, but not of PGE2. This suggests a predominant involvement of the phospholipase C pathway in the acute response to PGF(2α) and PGI2. A 3-h infusion of PGF(2α) produced a plateau of P4 release, even at the end of infusion. Simultaneous infusion of PGF(2α) and LH resulted in a profile similar to that obtained with PGF(2α) alone. When all possible combinations of PGF(2α), PGE2, and PGI2 were applied, the only remarkable effect was that PGF(2α) acted additively with PGE2 on release of OT. During the estrous cycle, each PG induced a different response at each stage; PGF(2α) was more stimulative with regard to P4 release from early to mid-luteal phase than at the late luteal phase, but was a constant stimulator for OT release throughout the luteal phase; PGE2 was the most stimulative at the mid-luteal phase; PGI2 was inhibitory at the early luteal phase but stimulatory at the mid-luteal phase; all three PGs were almost ineffective with respect to P4 release at the late luteal phase. We conclude that with respect to P4 and OT release from bovine CL during the estrous cycle in vitro, PGs act acutely, but differently. Overall results suggest that cell-to-cell contact may be a key function for acute CL release of OT in response to PGs in vitro; they suggest also that the actions and roles of PGs in the bovine CL may be much more complicated than has thus far been thought.

Original languageEnglish
Pages (from-to)423-430
Number of pages8
JournalBiology of Reproduction
Volume49
Issue number2
DOIs
StatePublished - 1993

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