Relationship between progesterone, oestrone sulphate and cortisol and the components of renin angiotensin aldosterone system in Spanish purebred broodmares during pregnancy.

This research attempts to clarify the relationship between particular hormones (progesterone, estrone, and cortisol) and the renin angiotensin aldosterone system (RAAS) among pregnant Spanish broodmares. It found that these interactions varied and suggested that other mechanisms apart from these hormones may influence RAAS during pregnancy.

Research Objectives

• The study sought to explore the relationship between certain reproductive hormones (progesterone, estrone, and cortisol) and components of the renin angiotensin aldosterone system (RAAS) in pregnant Spanish broodmares.
• It is known that the interaction between RAAS and reproductive hormones influences fetal and placental development during pregnancy, but such interactions were hitherto unclear in broodmares.

Research Methodology

• The study collected monthly venous blood samples from 31 Spanish broodmares aged between 5 and 15 years over the course of an 11-month pregnancy.
• Various hormone levels were analyzed using competitive immunoassay, a technique used for quantifying specific proteins or other substances through their properties as antigens or antibodies.

Findings

• The study discovered an increase in renin (REN) and aldosterone (ALD), a decrease in cortisol (CORT) levels, variable fluctuations in progesterone (P4) and estrone (OESTRONE), and no changes in angiotensin II (ANG-II) concentrations in these pregnant broodmares.
• No correlation was found between serum progesterone and either aldosterone or cortisol. Additionally, the estrone and renin levels were not correlated.
• However, there was a positive correlation between estrone and aldosterone levels. This suggests that the stimulation of the RAAS in normal pregnancy among these mares is not fully dependent on changes in progesterone and cortisol concentrations.
• Despite this, estrone does contribute to the secretion of aldosterone. This positions estrogen in a role involving aldosterone’s secretion through a mechanism not entirely dependent on renin.

Conclusions

• The lack of a competitive mechanism between aldosterone, cortisol, and progesterone during pregnancy in these Spanish mares suggests other, yet unknown, mechanisms at play apart from these hormones.
• This research indicates a need to understand these other mechanisms and how they interact with the RAAS during pregnancy in Spanish broodmares.