Urinary excretion of aquaporin-2 in patients with diabetes insipidus.

Abstract

BACKGROUND:

Urine-concentrating ability is regulated by vasopressin. Recently, the specific water-channel protein of the renal collecting duct, known as aquaporin-2, was cloned. However, it is not certain whether this molecule is responsive to vasopressin.

METHODS:

We measured the urinary excretion of aquaporin-2 and its response to vasopressin in 11 normal subjects and 9 patients with central or nephrogenic diabetes insipidus. The urine samples were collected during periods of dehydration and hydration and after the administration of vasopressin. Urine samples were analyzed for aquaporin-2 by the Western blot assay and immunogold labeling, and the amount of aquaporin-2 was determined by radioimmunoassay.

RESULTS:

Aquaporin-2 was detectable in the urine in both soluble and membrane-bound forms. In the five normal subjects tested, the mean (+/- SE) urinary excretion of aquaporin-2 was 11.2 +/- 2.2 pmol per milligram of creatinine after a period of dehydration, and it decreased to 3.9 +/- 1.9 pmol per milligram of creatinine (P = 0.03) during the second hour after a period of hydration. In the six other normal subjects, an infusion of desmopressin (1-desamino-8-D-arginine vasopressin) increased the urinary excretion of aquaporin-2 from 0.8 +/- 0.3 to 11.2 +/- 1.6 pmol per milligram of creatinine (P < 0.001). The five patients with central diabetes insipidus also had increases in urinary excretion of aquaporin-2 in response to the administration of vasopressin, but the four patients with X-linked or non-X-linked nephrogenic diabetes insipidus did not.

CONCLUSIONS:

Aquaporin-2 is detectable in the urine, and changes in the urinary excretion of this protein can be used as an index of the action of vasopressin on the kidney.

• Authors: K Kanno, S Sasaki, Y Hirata, S Ishikawa, K Fushimi, S Nakanishi, D G Bichet, F Marumo
• Journal: The New England journal of medicine (N Engl J Med) Vol. 332 Issue 23 Pg. 1540-5 (Jun 08 1995) ISSN: 0028-4793 [Print] United States
• PMID: 7537863 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• AQP2 protein, human
• Aquaporin 2
• Aquaporin 6
• Aquaporins
• Ion Channels
• Deamino Arginine Vasopressin

Topics

• Adult
• Aged
• Aquaporin 2
• Aquaporin 6
• Aquaporins
• Blotting, Western
• Case-Control Studies
• Deamino Arginine Vasopressin (pharmacology)
• Diabetes Insipidus (genetics, urine)
• Female
• Humans
• Ion Channels (urine)
• Kidney (drug effects, physiology)
• Male
• Middle Aged
• Radioimmunoassay