Objectives: 

In cyclic females of diverse species, the components of the renin angiotensin aldosterone system (RAAS) are closely related to specific reproductive functions that take place during the estrous cycle, as folliculogenesis, oocyte maturation, ovulation and corpus luteum development among others (Sneeringer et al., 2011). Until now these mechanisms remain unknown in the mare. The objective of this research was to analyze the changes experienced by REN concentrations along estrous cycle in Spanish Purebred mares.

Materials: 

This research was approved by the animal ethics committee of the CEU-Cardenal Herrera University. The study was carried out on 24 healthy Spanish Purebred mares aged between 4 and 17 years. Venous blood samples were taken daily during the period -5 to +5 of the estrous cycle, considering the time 0, the day of ovulation detected by ultrasound guidance. Serum REN concentrations were determined by competitive immunoassay.

Results: 

Significant rise of REN levels was observed one day before (1.62±0.51 pg/ml), reaching the maximum level (2.44±0.55 pg/ml) on the day of ovulation (p<0.05). After a significant drop in three days, there was a further increase to day +5 (1.09±0.15 pg/ml).

Conclusions: 

The results of this study reveal that like other species in cycling females, including women, REN is elevated during oestrous cycle and these elevations could be related with the ovulatory process during the follicular phase and the establishment of the corpus luteum in the luteal phase in Spanish Purebred mares.