Central regulation of body fluid homeostasis

• Published in: Proceedings of the Japan Academy, Series B Vol. 98; no. 7; pp. 283 - 324
• Main Authors: NODA, Masaharu, MATSUDA, Takashi
• Format: Journal Article
• Language: English
• Published: Ueno Park The Japan Academy 29.07.2022
• Subjects: [Na+] sensor; Aldosterone; Angiotensin; Angiotensin II; Blood pressure; body fluid homeostasis; Body fluids; Brain; Cerebrospinal fluid; Electrolytes; Homeostasis; Hormones; Hypertension; Hypotonicity; Kidneys; Osmoregulation; osmosensor; Physiology; Review; Rodents; Salt; salt appetite; Sensors; thirst; Trauma; Vasopressin
• ISSN: 0386-2208; 1349-2896
• DOI: 10.2183/pjab.98.016

Extracellular fluids, including blood, lymphatic fluid, and cerebrospinal fluid, are collectively called body fluids. The Na+ concentration ([Na+]) in body fluids is maintained at 135–145 mM and is broadly conserved among terrestrial animals. Homeostatic osmoregulation by Na+ is vital for life because severe hyper- or hypotonicity elicits irreversible organ damage and lethal neurological trauma. To achieve “body fluid homeostasis” or “Na homeostasis”, the brain continuously monitors [Na+] in body fluids and controls water/salt intake and water/salt excretion by the kidneys. These physiological functions are primarily regulated based on information on [Na+] and relevant circulating hormones, such as angiotensin II, aldosterone, and vasopressin. In this review, we discuss sensing mechanisms for [Na+] and hormones in the brain that control water/salt intake behaviors, together with the responsible sensors (receptors) and relevant neural pathways. We also describe mechanisms in the brain by which [Na+] increases in body fluids activate the sympathetic neural activity leading to hypertension.