Modulation of the renin-angiotensin-aldosterone system by steroid hormones during the oestrous cycle in mares.

This study investigates the relationship of steroid hormones with the renin-angiotensin-aldosterone system (RAAS) in mares during an oestrous cycle, finding correlations between these hormones and the activity of the RAAS around the time of ovulation.

Objective of the Study

• The purpose of this research was to examine how three steroid hormones – oestradiol-17β, progesterone, and cortisol – interact with components of the Renin-angiotensin-aldosterone system (RAAS) during the oestrous cycle in mares.

Methodology and Findings

• The study was conducted with 23 mares over the course of an oestrous cycle.
• Different components of the RAAS, including renin, angiotensin and aldosterone, as well as the three hormones under consideration, were measured during both the preovulatory and postovulatory periods.
• During the preovulatory period, significant positive correlations were observed between oestradiol-17β and renin and aldosterone concentrations, signifying that as levels of oestradiol-17β rose, so did levels of these components of the RAAS.
• Moreover, negative correlations were detected between progesterone and both renin and aldosterone levels, indicating that an increase in progesterone saw a decrease in these elements of the RAAS.
• In the postovulatory phase, researchers found positive correlations between concentrations of oestradiol-17β and angiotensin. Conversely, as progesterone levels increased, angiotensin levels decreased, as evidenced by a negative correlation.
• No correlation was discovered between cortisol concentrations and RAAS hormones, regardless of the ovulation stage.

Implications of the Research

• This research supports the idea that steroid hormones, namely oestradiol-17β and progesterone, exert an influence on the activity of the RAAS in mares around the time of ovulation.
• These findings are consistent with what is known from other species, including women and various laboratory animals.
• This study therefore deepens our understanding of how hormonal changes during the oestrous cycle modulate the RAAS, with potential implications for managing reproductive and related metabolic processes in mares and potentially other species.