title: Molecular cloning of urea transporters from the kidneys of baleen and toothed whales.
abstract: Urea transport in the kidney is important for the production of concentrated urine. This process is mediated by urea transporters (UTs) encoded by two genes, UT-A (Slc14a2) and UT-B (Slc14a1). Our previous study demonstrated that cetaceans produce highly concentrated urine than terrestrial mammals, and that baleen whales showed higher concentrations of urinary urea than sperm whales. Therefore, we hypothesized that cetaceans have unique actions of UTs to maintain fluid homeostasis in marine habitat. Kidney samples of common minke (Balaenoptera acutorostrata), sei (B. borealis), Bryde's (B. brydei) and sperm whales (Physeter macrocephalus) were obtained to determine the nucleotide sequences of mRNAs encoding UT. The sequences of 2.5-kb cDNAs encode 397-amino acid proteins, which are 90-94% identical to the mammalian UT-A2s. Two putative glycosylation sites are conserved between the whales and the terrestrial mammals, whereas consensus sites for protein kinases are not completely conserved; only a single protein kinase A consensus site was identified in the whale UT-A2s. Two protein kinase C consensus sites are present in the baleen whale UT-A2s, however, a single protein kinase C consensus site was identified in the sperm whale UT-A2. These different phosphorylation sites of whale UT-A2s may result in the high concentrations of urinary urea in whales, by reflecting their urea permeability.
authors.affiliation: Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan. birukawa@imcj-gdt.jp
authors.forename: Naoko
authors.initials: N
authors.lastname: Birukawa
authors.forename: Hironori
authors.initials: H
authors.lastname: Ando
authors.forename: Mutsuo
authors.initials: M
authors.lastname: Goto
authors.forename: Naohisa
authors.initials: N
authors.lastname: Kanda
authors.forename: Luis A
authors.initials: LA
authors.lastname: Pastene
authors.forename: Akihisa
authors.initials: A
authors.lastname: Urano
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000302:isolation & purification; D007668:Kidney / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D010802:Phylogeny; D012333:RNA, Messenger / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D014907:Whales / Q000235:genetics* / Q000378:metabolism; D000096982:Urea Transporters
chemical_list: D018076:DNA, Complementary; D026901:Membrane Transport Proteins; D012333:RNA, Messenger; D000096982:Urea Transporters