Proliferative processes within the equine corpus luteum may depend on paracrine progesterone actions.

The research paper investigates the role of progesterone hormone in the angiogenic activity and prostaglandin E(2) (PGE(2)) and nitric oxide (NO) production in the corpus luteum (a temporary endocrine structure involved in ovulation and early pregnancy stages) of mares.

Objective of the Research

• The study primarily seeks to explore if progesterone (P(4)) has an autocrine or paracrine effect on luteal angiogenic activity and the production of P(4), PGE(2), and NO in mares’ corpus luteum.

Methods Employed

• The research was conducted using corpora hemorrhagica (CH) and mid-luteal phase corpus luteum (MCL) and four treatment conditions were applied: i) Without any hormone (Control); ii) Treated with P(4); iii) Treated with P(4) precursor – pregnenolone; iv) Treated with a P(4) antagonist-onapristone.

Findings of the Study

• When MCLs were treated with P(4) and pregnenolone, the NO production was found to decrease compared to the CH treatment group.
• The research also showed an increase in PGE(2) levels when moved from CH to MCL. There was also a trend of elevated PGE(2) with pregnenolone treated luteal tissues.
• In the CH, the application of pregnenolone led to a decrease in P(4) levels compared to control, P(4), onapristone, and pregnenolone.
• Within MCL, the treatment with pregnenolone resulted in a decrease and P(4) tended to decrease in bovine aortic endothelial cell (BAEC) mitogenesis.
• The P(4) antagonist, Onapristone, tended to augment BAEC proliferation relative to P(4).

Conclusion of the Study

• The research concludes that there was no direct impact of the treatments on BAEC. This suggests that the prolonged effect of P(4) and its precursor may inhibit the production of angiogenic factors by the equine MCL, leading it towards functional and structural regression of the corpus luteum.