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. Author manuscript; available in PMC: 2015 Jul 29.
Published in final edited form as: Physiol Rev. 2012 Oct;92(4):1577–1617. doi: 10.1152/physrev.00009.2012

Figure 15. Regulation of blood volume through distal Na+ reabsorption and blood vessel constriction.

Figure 15

Mild hypovolemia through decreases in the glomerular filtration rate (GFR) results in activation of the renin-angiotensin-aldosterone system. Aldosterone, which is released by the adrenal gland, activates ENaC in the collecting duct and through WNK4/SPAK, also activates the Na-Cl cotransporter in the distal convoluted tubule. AngII activates NCC through SPAK/OSR1, and also affects contractility of blood vessels. Severe hypovolemia (or small rises in plasma osmolarity) leads to the release of arginine-vasopressin (AVP or ADH) from the pituitary gland, resulting in the constriction of blood vessels, insertion of water channels in collecting duct epithelial cells, and activation of NCC (blue arrows).