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Molecular and functional characterization of a vasotocin-sensitive aquaporin water channel in quail kidney
- Source :
- American Journal of Physiology-Regulatory, Integrative and Comparative Physiology. 287:R915-R924
- Publication Year :
- 2004
- Publisher :
- American Physiological Society, 2004.
-
Abstract
- Both mammals and birds can concentrate urine hyperosmotic to plasma via a countercurrent multiplier mechanism, although evolutionary lines leading to mammals and birds diverged at an early stage of tetrapod evolution. We reported earlier (Nishimura H, Koseki C, and Patel TB. Am J Physiol Regul Integr Comp Physiol 271: R1535–R1543, 1996) that arginine vasotocin (AVT; avian antidiuretic hormone) increases diffusional water permeability in the isolated, perfused medullary collecting duct (CD) of the quail kidney. In the present study, we have identified an aquaporin (AQP) 2 homolog water channel in the medullary cones of Japanese quail, Coturnix coturnix (qAQP2), by RT-PCR-based cloning techniques. A full-length cDNA contains an 822-bp open reading frame that encodes a 274-amino acid sequence with 75.5% identity to rat AQP2. The qAQP2 has six transmembrane domains, two asparagine-proline-alanine (NPA) sequences, and putative N-glycosylation (asparagine-124) and phosphorylation sites (serine-257) for cAMP-dependent protein kinase. qAQP2 is expressed in the membrane of Xenopus laevis oocytes and significantly increased its osmotic water permeability (Pf), inhibitable ( P < 0.01) by mercury chloride. qAQP2 mRNA (RT-PCR) was detected in the kidney; medullary mRNA levels were higher than cortical levels. qAQP2 protein that binds to rabbit anti-rat AQP2 antibody is present in the apical/subapical regions of both cortical and medullary CDs from normally hydrated quail, and the intensity of staining increased only in the medullary CDs after water deprivation or AVT treatment. The relative density of the ∼29-kDa protein band detected by immunoblot from the medullary cones was modestly higher in water-deprived/AVT-treated quail. The results suggest that 1) medullary CDs of quail kidneys express a mercury-sensitive functioning qAQP2 water channel, and 2) qAQP2 is at least partly regulated by an AVT-dependent mechanism. This is the first clear identification of AQP2 homolog in nonmammalian vertebrates.
- Subjects :
- Male
DNA, Complementary
Physiology
Xenopus
Blotting, Western
Molecular Sequence Data
Countercurrent multiplication
Aquaporin
Vasotocin
Coturnix
Biology
Aquaporins
Kidney
Quail
Permeability
chemistry.chemical_compound
Osmotic Pressure
Physiology (medical)
biology.animal
medicine
Animals
Amino Acid Sequence
Cloning, Molecular
DNA Primers
Water Deprivation
Osmotic concentration
Reverse Transcriptase Polymerase Chain Reaction
Immunohistochemistry
medicine.anatomical_structure
Biochemistry
chemistry
Water channel
Oocytes
RNA
Electrophoresis, Polyacrylamide Gel
Female
Medullary cone
Algorithms
Subjects
Details
- ISSN :
- 15221490 and 03636119
- Volume :
- 287
- Database :
- OpenAIRE
- Journal :
- American Journal of Physiology-Regulatory, Integrative and Comparative Physiology
- Accession number :
- edsair.doi.dedup.....1a3d18858258d28cd7c4b0f830dc6518