Down-regulation of urinary AQP2 and unaffected response to hypertonic saline after 24 hours of fasting in humans

Twenty-four hours of fasting decreased u-AQP2 and reduced urine osmolality likely as a result of decreased sensitivity of collecting duct cells to AVP. Fasting-related insensitivity of collecting duct cells to AVP was restored by 3% saline infusion. Finallly, after saline infusion, other factors such as the increased plasma atrial natriuretic peptide (p-ANP) levels could contribute to the u-AQP2 regulation.