Activation of ENaC by AVP Contributes to Urinary Concentrating Mechanism and Dilution of Plasma.

Activation of ENaC by AVP Contributes to Urinary Concentrating Mechanism and Dilution of Plasma. Am J Physiol Renal Physiol. 2014 Nov 12;:ajprenal.00246.2014 Authors: Mironova E, Chen Y, Pao AC, Roos KP, Kohan DE, Bugaj V, Stockand JD Abstract Vasopressin (AVP) activates the epithelial Na+ channel (ENaC). The physiological significance of this activation is unknown. The current studies test if activation of ENaC contributes to AVP-sensitive urinary concentration. Consumption of a 3% NaCl solution induced hypernatremia and plasma hypertonicity in mice. Plasma [AVP] and urine osmolality increased in hypernatremic mice in an attempt to compensate for increases in plasma tonicity. ENaC activity was elevated in mice consuming 3% NaCl solution compared to mice consuming a diet enriched in Na+ with ad libitum tap water. The latter diet does not cause hypernatremia. To determine whether the increase in ENaC activity in mice consuming 3% NaCl solution served to compensate for hypernatremia, mice were treated with the ENaC inhibitor benzamil. Co-administration of benzamil with 3% NaCl solution decreased urinary osmolality and increased urine flow so that urinary Na+ excretion increased with no effect on urinary [Na+]. This decrease in urinary concentration further increased plasma [Na+], osmolality, and [AVP] in these already hypernatremic mice. Benzamil similarly compromised urinary concentration in water deprived mice and in mice treated wit...
Source: Am J Physiol Renal P... - Category: Urology & Nephrology Authors: Tags: Am J Physiol Renal Physiol Source Type: research