Central angiotensin‐(1–7) increases osmotic thirst

Abstract

What is the central question of this study? The central goal of this study was to understand the effects of central angiotensin-(1-7) on basal and osmotically stimulated water intake in rats. What is the main finding and its importance? This study demonstrated that central administration of angiotensin-(1-7) did not induce thirst in basal conditions but increased water intake after osmotic stimulation, such as water deprivation and salt loading. These results indicate a new function for this peptide, which, in turn, allows for future research on the mechanisms through which angiotensin-(1-7) influences osmotic thirst. Angiotensin-(1-7) [Ang-(1-7)] is generated by type 2 angiotensin-converting enzyme (ACE2) and binds to the MAS receptor. Although it is well known that Ang-(1-7) functionally antagonizes the effects of the classical renin-angiotensin system in several situations, the role of Ang-(1-7) in hydromineral homeostasis is not clear. The aim of this study was to assess the role of Ang-(1-7) on neuroendocrine responses to hyperosmolality in rats. Male Wistar rats were divided into the following three groups: control; 24 h of water deprivation (WD); and 24 h of salt loading (SL; 1.8% NaCl). Intracerebroventricular (i.c.v.) injections of Ang-(1-7) or vehicle were given to assess water intake and plasma concentration of vasopressin. Additionally, the brains from control and WD groups were collected to evaluate gene expression in the subfornical organ (SFO), paraventricular nucleus (PVN) and supraoptic nucleus (SON). It was found that i.c.v. Ang-(1-7) did not change water and salt intake in control rats; however, Ang-(1-7) increased water intake after WD and SL, with no change in salt intake. Plasma vasopressin was not changed by i.c.v. Ang-(1-7) in control or WD rats. Moreover, WD increased Mas gene expression in the SON and PVN, with no changes in Ace2 mRNA levels. In conclusion, Ang-(1-7) increases thirst after osmotic stimuli, indicating that a previous sensitization to its action is necessary. This finding is consistent with the increased Mas gene expression in the PVN and SON after water deprivation.

Differential Diagnosis of COVID-19: Importance of Measuring Blood Lymphocytes, Serum Electrolytes, and Olfactory and Taste Functions

“…ACE2 also play an important role to maintain fluid and electrolyte balance, because ACE2 changes Ang II to Ang-(1-7) (Cohen et al 2020). Additionally, Dos-Santos et al (2017) showed that intracerebroventricular injection of Ang-(1-7) increased water intake after osmotic stimulates. Furthermore, SARS-CoV-2 induces downregulation of ACE2 expression and shedding from the cell surface, resulting in an increase of Ang II and a decrease of Ang-(1-7) (Cohen et al 2020).…”

“…Furthermore, SARS-CoV-2 induces downregulation of ACE2 expression and shedding from the cell surface, resulting in an increase of Ang II and a decrease of Ang-(1-7) (Cohen et al 2020). These suggest that serum electrolyte balance is affected by COVID-19, although the effect of Ang-(1-7) on serum electrolytes is unclear (Dos-Santos et al 2017). Lippi et al (2020) found that the levels of sodium, potassium, and calcium in severe COVID-19 patients were significantly higher than those in non-severe patients.…”

Hemodynamic phenotyping of transgenic rats with ubiquitous expression of an angiotensin-(1-7)-producing fusion protein

“…Joyner et al [69] using intravenous infusion of the MAS antagonist, A779, in pregnant rats suggested that Ang-(1-7) contributes to enhance water intake during pregnancy. In addition, dos Santos et al [70] showed that after water deprivation or salt loading, ICV Ang-(1-7) increased water intake. The expression of MAS in the parvocellular area of PVN and in other nuclei that control water intake [1,39] form the basis to support a dipsogenic effect of Ang-(1-7), at least in particular conditions.…”

Chromosome-level Genome Assembly of Acanthopagrus latus Provides Insights into Salinity Stress Adaptation of Sparidae

“…For example, angiotensin-converting enzyme 2, as a carboxymonopeptidase, catalyzes angiotensin II conversion to angiotensin 1-7. Previous studies have reported that angiotensin 1-7 doesn't induce thirst in basal conditions but increased water intake after osmotic stimulation, such as water deprivation and salt loading in rats (Dos-Santos et al 2017). The positive selected ACE2 may implicit that A. latus could maintain the osmotic and cell volume homeostasis by regulating the activity of ACE2.…”