Pediatric Nephrology

, Volume 13, Issue 5, pp 379–390

Ovine aquaporin-2: cDNA cloning, ontogeny and control of renal gene expression

  • A. Butkus
  • L. Earnest
  • K. Jeyaseelan
  • K. Moritz
  • H. Johnston
  • N. Tenis
  • E. M. Wintour
EXPERIMENTAL STUDIES / ORIGINAL ARTICLE

DOI: 10.1007/s004670050627

Cite this article as:
Butkus, A., Earnest, L., Jeyaseelan, K. et al. Pediatr Nephrol (1999) 13: 379. doi:10.1007/s004670050627

Abstract

 The aim of this study was to test the hypothesis that the relative insensitivity of the ovine fetal kidney to arginine vasopressin (AVP) is due to low levels of expression of the gene for aquaporin-2 (AQP2) which encodes the AVP-regulated water channel. We report the cloning of the cDNA for the ovine AQP2 which has a major transcript at 4.2 kilobases (kb) and a minor transcript at 1.5 kb, resembling the human gene transcripts. At 40–60 days’ (term = 145–150 days’), mRNA levels are very low, detectable only by reverse transcription-polymerase chain reaction (RT-PCR). By Northern blot analysis AQP2 mRNA is detectable at 75 days’. The ratio of AQP2/glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA increases approximately 2.4-fold between 100 and 140 days’ when it is about 41% of adult values. Both glucocorticoids and the renin-angiotensin system are involved in maturation of renal function. When fetuses at 75 or 85 days of gestation were exposed to high levels of dexamethasone for 2–3 days, mRNAs for both GAPDH and AQP2 doubled, but the ratio was unchanged. Angiotensin I, infused for 3 days at 115–120 days’ gestation, increased the AQP2/GAPDH mRNA ratios by twofold (major transcript) and sixfold (minor transcript), which were highly significant (P<0.001). The increasing sensitivity of the ovine fetal kidney to AVP, from 100–140 days of gestation, is largely due to increasing AQP2 gene expression over this period.

Key words Aquaporin-2 Ovine fetal kidney Arginine vasopressin 

Copyright information

© IPNA - International Pediatric Nephrology Association New York, USA 1999

Authors and Affiliations

  • A. Butkus
    • 1
  • L. Earnest
    • 2
  • K. Jeyaseelan
    • 3
  • K. Moritz
    • 2
  • H. Johnston
    • 2
  • N. Tenis
    • 2
  • E. M. Wintour
    • 2
  1. 1.Department of Anatomy and Cell Biology, University of Melbourne, Parkville, Victoria, AustraliaAU
  2. 2.Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Parkville, Victoria, 3052, Australia Tel.: +61-3-9344-4664, Fax: +61-3-9348-1707AU
  3. 3.Department of Biochemistry, National University of Singapore, Singapore, 0511SG

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