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Proc Biol Sci 2012 Dec 07;2791748:4795-802. doi: 10.1098/rspb.2012.1945.
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The epithelial sodium channel in the Australian lungfish, Neoceratodus forsteri (Osteichthyes: Dipnoi).

Uchiyama M , Maejima S , Yoshie S , Kubo Y , Konno N , Joss JM .

Epithelial sodium channel (ENaC) is a Na(+)-selective, aldosterone-stimulated ion channel involved in sodium transport homeostasis. ENaC is rate-limiting for Na(+) absorption in the epithelia of osmoregulatory organs of tetrapods. Although the ENaC/degenerin gene family is proposed to be present in metazoans, no orthologues or paralogues for ENaC have been found in the genome databases of teleosts. We studied full-length cDNA cloning and tissue distributions of ENaCα, β and γ subunits in the Australian lungfish, Neoceratodus forsteri, which is the closest living relative of tetrapods. Neoceratodus ENaC (nENaC) comprised three subunits: nENaCα, β and γ proteins. The nENaCα, β and γ subunits are closely related to amphibian ENaCα, β and γ subunits, respectively. Three ENaC subunit mRNAs were highly expressed in the gills, kidney and rectum. Amiloride-sensitive sodium current was recorded from Xenopus oocytes injected with the nENaCαβγ subunit complementary RNAs under a two-electrode voltage clamp. nENaCα immunoreactivity was observed in the apical cell membrane of the gills, kidney and rectum. Thus, nENaC may play a role in regulating sodium transport of the lungfish, which has a renin-angiotensin-aldosterone system. This is interesting because there may have been an ENaC sodium absorption system controlled by aldosterone before the conquest of land by vertebrates.

PubMed ID: 23055064
PMC ID: PMC3497098
Article link: Proc Biol Sci

References [+] :
Alvarez de la Rosa, Structure and regulation of amiloride-sensitive sodium channels. 2000, Pubmed