Cellular localization of a putative Na+/H+ exchanger 3 during ontogeny in the pronephros and mesonephros of the Japanese black salamander (Hynobius nigrescens Stejneger)

Abstract

The cloning of cDNA and an examination of the tissue distribution of Na(+)/H(+) exchanger 3 (NHE3) were carried out in the Japanese black salamander, Hynobius nigrescens. The cellular localization of Hynobius NHE3 was examined by in situ hybridization and immunohistochemistry during ontogeny in the nephron of the pronephros and mesonephros of the salamander. The partial amino acid sequence of Hynobius NHE3 was 81% and 72% identical to rat NHE3 and stingray NHE3, respectively. Hynobius NHE3 mRNA and protein were exclusively expressed along the late portion of the distal tubule to the anterior part of the pronephric duct of premetamorphic larvae (IY stages 43-50). NHE3 mRNA was expressed in the pronephros but not in the external gills in the larvae at the digit differentiation stage (IY stage 50). In the adult, mRNA was strongly expressed in the mesonephros but not in the ventral and dorsal skin. In juvenile and adult specimens, NHE3 immunoreactivity was observed at the apical membrane of the initial parts of the distal tubules of the mesonephric kidney. Immunohistochemical and in situ hybridization studies suggested that Na(+) absorption coupled with H(+) secretion via NHE3 occurred in the distal nephron of the pronephros and mesonephros. This is the first study to indicate NHE3 expression during ontogeny in amphibians.

African lungfish,Protopterus annectens, possess an arginine vasotocin receptor homologous to the tetrapod V2-type receptor

“…Anti-vacuolar type H + -ATPase α-subunit antiserum was raised by immunizing Japanese white rabbits with a synthetic peptide, NH 2 -AEMPADSGYPAYLGAR-COOH, as described previously (Hayashi et al, 2000). This antiserum specifically recognizes intercalated cells of the late distal tubule and the collecting duct of the amphibian kidney (Uchiyama and Yoshizawa, 2002;Konno et al, 2006;Konno et al, 2007;Kumano et al, 2008).…”

Ontogeny of ENaC expression in the gills and the kidneys of the Japanese black salamander (Hynobius nigrescens Stejneger)

“…The mesonephric nephron of the Japanese black salamander was previously investigated in detail (Kumano et al, 2008). ENaCα immunoreactivity was observed in the apical cell membrane of the late distal tubule (Fig.…”

“…Using double immunostaining of ENaCα and the vacuolar‐type H + ‐ATPase, this study showed immunohistochemically that Hynobius ENaC α‐subunit protein and vacuolar‐type H + ‐ATPase are localized in the apical membrane of principal cells and intercalated cells, respectively, along the late segment of the distal tubule to collecting duct in the kidney of H. nigrescens as well as in the toad kidney (Konno et al, 2007). Our previous study showed that NHE3 mRNA and protein were only present in early segment of the distal nephron in H. nigrescens (Kumano et al, 2008). Taken together, this study demonstrates that transepithelial sodium transport in the late distal nephron occurs principally via NHE3 and ENaC in early and late segments of the distal tubule of H. nigrescens , respectively.…”

“…The Xenopus pronephric distal nephron has at least two subdomains demarcated by the expression of Na + /K + /2Cl − cotransporter in the early domain and xNBC in the late domain (Zhou and Vize, 2004). We observed that Na + /H + exchange transporter 3 (NHE3) only occurs in the anterior portion of the pronephric duct in the salamander larva (Kumano et al, 2008). In the present immunohistochemical study, ENaCα was expressed specifically in the epithelial cells of the pronephric duct but not other segments in the pronephros at the IY stage 50 larvae.…”

“…We recently observed the presence of Na + ,K + ‐ATPase, vacuolar‐type H + ‐ATPase and sodium and proton exchanger 3 (NHE3) in the distal tubules of pronephros and mesonephros of the salamander. In the external gills of the salamander, a putative NHE3‐mRNA and protein were not present although there is a possibility that other type of NHEs may present (Kumano et al, 2008). Meanwhile, as far as we know, there is no evidence for the presence of ENaC protein in the gills of amphibians.…”