Scientific Evidences Supporting the Activation of the Renin-Angiotensin-Aldosterone System during Estral Cycle and Pregnancy in Mares

In women and laboratory animals, local and circulating components of the renin-angiotensin-aldosterone system (RAAS) are related to specific reproductive functions that occur during the estrous cycle, such as folliculogenesis, ovulation, corpus luteum development, and steroidogenesis. Also, in pregnant females of these species, maternal cardiovascular and renal systems undergo intense modifications, with the aim of matching the increased energy requirements of the fetus and fetoplacental unit. Some of these changes can be the origin, and others the consequence of a new endocrine environment. The fetus and the placenta induce endocrine changes, with modifications in the protein, lipid, carbohydrate, and mineral metabolism, together with simultaneous cardiovascular changes derived from the uterine growth and its content. The participation of RAAS during this period is of vital importance to regulate these cardiovascular, hemodynamic, hematological, and metabolic adjustments imposed by pregnancy because they will have a direct influence on the correct development and viability of the fetus. In mares, our research team has been investigating the changes of RAAS in mares during the estral cycle and during pregnancy, and these results are presented in the current chapter, comparing with the data previously reported for women and laboratory animals.