Molecular characterization of a urea transporter in the gill of the gulf toadfish (Opsanus beta)

Patrick J. Walsh, Molly J. Heitz, Catherine E. Campbell, Gordon J. Cooper, Monica Medina, Yuxiang S. Wang, Greg G. Goss, Vladimir Vincek, Chris M. Wood, Craig P. Smith

Research output: Contribution to journalArticle

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Abstract

Urea excretion by the gulf toadfish (Opsanus beta) has been shown in previous studies to be a highly pulsatile facilitated transport, with excretion probably occurring at the gill. The present study reports the isolation of an 1800 base pair (kb) cDNA from toadfish gill with one open reading frame putatively encoding a 475-residue protein, the toadfish urea transporter (tUT). tUT, the first teleostean urea transporter cloned, has high homology with UTs (facilitated urea transporters) cloned from mammals, an amphibian and a shark, and most closely resembles the UT-A subfamily. When expressed in Xenopus laevis oocytes, tUT increased urea permeability (as measured by [14C]urea uptake) five- to sevenfold, and this permeability increase was abolished by phloretin, a common inhibitor of other UTs. Northern analysis using the 1.8 kb clone was performed to determine the tissue distribution and dynamics of tUT mRNA expression. Of six tissues examined (gill, liver, red blood cells, kidney, skin and intestine), only gill showed expression of tUT mRNA, with a predominant band at 1.8 kb and a minor band at 3.5 kb. During several points in the urea pulse cycle of toadfish (0, 4, 6, 12 and 18 h post-pulse), measured by excretion of [14C]urea into the water, gill mRNA samples were obtained. Expression of tUT mRNA was found to be largely invariant relative to expression of β-actin mRNA over the pulse cycle. These results further confirm the gill localization of urea transport in the toadfish and suggest that tUT regulation (and the regulation of pulsatile urea excretion) is probably not at the level of mRNA control. The results are discussed in the context of the mechanisms of vasopressin-regulated UT-A in mammalian kidney and morphological data for the toadfish gill.

Original languageEnglish
Pages (from-to)2357-2364
Number of pages8
JournalJournal of Experimental Biology
Volume203
Issue number15
StatePublished - Aug 1 2000

Fingerprint

Batrachoidiformes
urea
transporters
gills
Batrachoididae
Urea
Messenger RNA
excretion
Opsanus beta
urea transporter
gulf
Permeability
Phloretin
Kidney
Sharks
permeability
Xenopus laevis
Amphibians
Tissue Distribution

Keywords

  • Gill
  • Gulf toadfish
  • Nitrogen excretion
  • Opsanus beta
  • Urea transporter gene
  • UT-A2

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Agricultural and Biological Sciences (miscellaneous)

Cite this

Walsh, P. J., Heitz, M. J., Campbell, C. E., Cooper, G. J., Medina, M., Wang, Y. S., ... Smith, C. P. (2000). Molecular characterization of a urea transporter in the gill of the gulf toadfish (Opsanus beta). Journal of Experimental Biology, 203(15), 2357-2364.

Molecular characterization of a urea transporter in the gill of the gulf toadfish (Opsanus beta). / Walsh, Patrick J.; Heitz, Molly J.; Campbell, Catherine E.; Cooper, Gordon J.; Medina, Monica; Wang, Yuxiang S.; Goss, Greg G.; Vincek, Vladimir; Wood, Chris M.; Smith, Craig P.

In: Journal of Experimental Biology, Vol. 203, No. 15, 01.08.2000, p. 2357-2364.

Research output: Contribution to journalArticle

Walsh, PJ, Heitz, MJ, Campbell, CE, Cooper, GJ, Medina, M, Wang, YS, Goss, GG, Vincek, V, Wood, CM & Smith, CP 2000, 'Molecular characterization of a urea transporter in the gill of the gulf toadfish (Opsanus beta)', Journal of Experimental Biology, vol. 203, no. 15, pp. 2357-2364.
Walsh PJ, Heitz MJ, Campbell CE, Cooper GJ, Medina M, Wang YS et al. Molecular characterization of a urea transporter in the gill of the gulf toadfish (Opsanus beta). Journal of Experimental Biology. 2000 Aug 1;203(15):2357-2364.
Walsh, Patrick J. ; Heitz, Molly J. ; Campbell, Catherine E. ; Cooper, Gordon J. ; Medina, Monica ; Wang, Yuxiang S. ; Goss, Greg G. ; Vincek, Vladimir ; Wood, Chris M. ; Smith, Craig P. / Molecular characterization of a urea transporter in the gill of the gulf toadfish (Opsanus beta). In: Journal of Experimental Biology. 2000 ; Vol. 203, No. 15. pp. 2357-2364.
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