Figure 1.

Systemic and intra-cellular adaptive response to dehydration and subsequent extracellular/intracellular hyperosmolarity.

Humans have developed multi-layered protective mechanisms to counteract extracellular hyperosmolarity. For instance, they avoid water loss from the surface of the body is reduced by keratinized skin. Once extracellular hyperosmolarity is sensed by the central nervous system, the brain stimulates neuronal circuits activating water intake and secretion of the anti-diuretic hormone arginine vasopressin (AVP) from the posterior lobe of the pituitary gland to produce highly concentrated urine in the kidney. Oxytocin is also secreted in response to extracellular hyperosmolarity in rodents and induces natriuresis and hence excretion of electrolytes. Extracellular hyperosmolarity also stimulates/induces intracellular NFAT5 and activates a cellular adaptive response to osmotic stress, by inducing several osmotic stress-responsive genes and causing accumulation of organic osmolytes to equilibrate osmotic difference across the plasma membrane.

AVP: arginine vasopressin