Is endothelin-1 luteolytic or antiluteolytic in ewes?

Area of Science:

• Reproductive Endocrinology
• Ovine Physiology

Background:

• Endothelin-1 (ET-1) has been implicated in prostaglandin (PG) F(2)alpha-induced luteolysis.
• Prostaglandins E (PGE) are crucial for implantation and pregnancy recognition, exhibiting antiluteolytic and luteotropic properties.

Purpose of the Study:

• To investigate whether ET-1 administration is luteolytic in ewes.
• To determine the effect of ET-1 on corpus luteum weight, progesterone secretion, and the PGE:PGF(2)alpha ratio.

Main Methods:

• Ovine estrous cycles were manipulated, and ET-1 was infused either interstitially (IP) or intrauterine (IU) from day 10 to day 18.
• Control groups received vehicle infusions (Vehicle-IP, Vehicle-IU).
• Corpus luteum weights, jugular venous plasma progesterone profiles, and the PGE:PGF(2)alpha ratio were analyzed.

Main Results:

• ET-1 administration (IP or IU) significantly increased corpus luteum weights compared to vehicle controls.
• Progesterone levels were higher in ET-1 treated ewes than in controls.
• The PGE:PGF(2)alpha ratio was elevated in ET-1 treated ewes.

Conclusions:

• ET-1 is not luteolytic in ewes.
• ET-1 may exert luteotropic or antiluteolytic effects by modulating the uterine PGE:PGF(2)alpha ratio.
• These findings challenge the proposed role of ET-1 in mediating PGF(2)alpha-induced luteolysis.