**Abstract**

The hydromineral homeostasis is fundamental to survival due to maintenance constant the osmotic properties of the plasma and proper tissue perfusion pressure, being maintained primarily through the regulation of the ingestion and urinary excretion of water and electrolytes, mainly sodium. The Renin-Angiotensin System (RAS) plays an essential role in the maintenance of hydromineral homeostasis by eliciting sodium and water intake and by inducing sodium urinary retention through aldosterone release and hemodynamic effect via angiotensin II a key component of the RAS. The hypothalamus-pituitary system also plays a fundamental role in the maintenance of body fluid homeostasis by secreting vasopressin (AVP) and oxytocin (OT) in response to osmotic and non-osmotic, and volemic stimuli. Furthermore, some studies report that besides reproductive function and sexual behavior, ovarian gonadal hormones, mainly 17β-estradiol (E2), modulate other non-reproductive functions such as cardiovascular system, body fluid balance, mood, mental state, memory, and cognition. Estradiol is known to mediate hydromineral homeostasis and blood pressure mainly by attenuating RAS actions. On the other hand, estradiol modulates neurohypophysial hormones secretion in many different ways. In this chapter, we will discuss the main non-reproductive effects of E2 on the control of hydromineral homeostasis, focusing on ingestive behavior and neurohypophyseal hormonal release.

**Keywords:** angiotensin II, cell signaling, thirst, sodium appetite, vasopressin, oxytocin

### **1. Introduction**

Because sodium is the most abundant cation in the extracellular fluid (ECF) and is an osmotically effective ion, sodium body content is the pivotal determinant of ECF volume. Then, when sodium moves between extracellular and intracellular compartments, water moves together in favor of the osmotic gradient. The osmolality and volume of body fluids are maintained, respectively, through the regulation of the ingestion (gain) and urinary excretion (loss) of water and electrolytes, mainly sodium (for review see [1]). The constancy of the sodium concentration and the osmolality of extracellular body fluid are essential to hydromineral homeostasis

and are therefore fundamental to survival since is very important for proper tissue perfusion pressure and osmotic gradient across the cellular membrane [1].
