Shift of Chloride Cell Distribution during Early Life Stages in Seawater-Adapted Killifish, Fundulus heteroclitus

Marine cartilaginous fish retain a high concentration of urea to maintain the plasma slightly hyperosmotic to the surrounding seawater. In adult fish, urea is produced by hepatic and extrahepatic ornithine urea cycles (OUCs). However, little is known about the urea retention mechanism in developing cartilaginous fish embryos. In order to address the question as to the mechanism of urea-based osmoregulation in developing embryos, the present study examined the gene expression profiles of OUC enzymes in oviparous holocephalan elephant fish (Callorhinchus milii) embryos. We found that the yolk sac membrane (YSM) makes an important contribution to the ureosmotic strategy of the early embryonic period. The expression of OUC enzyme genes was detectable in the embryonic body from at least stage 28, and increased markedly during development to hatching, which is most probably due to growth of the liver. During the early developmental period, however, the expression of OUC enzyme genes was not prominent in the embryonic body. Meanwhile, we found that the mRNA expression of OUC enzymes was detected in the extra-embryonic YSM; the mRNA expression of cmcpsIII in the YSM was much higher than that in the embryonic body during stages 28-31. Significant levels of enzyme activity and the existence of mitochondrial-type cmgs1 transcripts in the YSM supported the mRNA findings. We also found that the cmcpsIII transcript is localized in the vascularized inner layer of the YSM. Taken together, our findings demonstrate for the first time that the YSM is involved in urea-based osmoregulation during the early to mid phase of development in oviparous cartilaginous fish.

Section: Research Articlesupporting

confidence: 54%

Urea-based osmoregulation in the developing embryo of oviparous cartilaginous fish (Callorhinchus milii): contribution of the extraembryonic yolk sac during the early developmental period

Takagi

Kajimura

Tanaka

et al. 2013

“…The specific antibody was affinity-purified and labeled with fluorescein isothiocyanate (FITC) as a fluorescent marker. The specificity of the antibody had been confirmed by western blot analysis (Katoh et al, 2000).…”

Section: Confocal Laser Scanning Microscopymentioning

confidence: 87%

“…The antiserum (NAK121) was raised in a rabbit against a synthetic peptide corresponding to part of the highly conserved region of the Na + /K + -ATPase α-subunit (Katoh et al, 2000), which was based on the method described by Ura et al (1996). The specific antibody was affinity-purified and labeled with fluorescein isothiocyanate (FITC) as a fluorescent marker.…”

Section: Confocal Laser Scanning Microscopymentioning

confidence: 99%

Vacuolar-type proton pump in the basolateral plasma membrane energizes ion uptake in branchial mitochondria-rich cells of killifishFundulus heteroclitus, adapted to a low ion environment

Katoh

Hyodo

Kaneko

2003

Self Cite

125

SUMMARYWe examined the involvement of mitochondria-rich (MR) cells in ion uptake through gill epithelia in freshwater-adapted killifish Fundulus heteroclitus, by morphological observation of MR cells and molecular identification of the vacuolar-type proton pump (V-ATPase). MR cell morphology was compared in fish acclimated to defined freshwaters with different NaCl concentrations: low (0.1 mmol l-1)-, mid (1 mmol l-1)-and high (10 mmol l-1)-NaCl environments. MR cells, mostly located on the afferent-vascular side of the gill filaments, were larger in low- and mid-NaCl environments than in the high-NaCl environment. Electron-microscopic observation revealed that the apical membrane of well-developed MR cells in low- and mid-NaCl environments was flat or slightly projecting, and equipped with microvilli to expand the surface area exposed to these environments. On the other hand, in the high-NaCl environment, the apical membrane was invaginated to form a pit, and MR cells often formed multicellular complexes with accessory cells, although the NaCl concentration was much lower than that in plasma. We cloned and sequenced a cDNA encoding the A-subunit of killifish V-ATPase. The deduced amino acid sequence showed high identity with V-ATPase A-subunits from other vertebrate species. Light-microscopic immunocytochemistry, using a homologous antibody, revealed V-ATPase-immunoreactivity in Na+/K+-ATPase-immunoreactive MR cells in low-NaCl freshwater, whereas the immunoreactivity was much weaker in higher NaCl environments. Furthermore, immuno-electron microscopy revealed V-ATPase to be located in the basolateral membrane of MR cells. These findings indicate that MR cells are the site responsible for active ion uptake in freshwater-adapted killifish, and that basolaterally located V-ATPase is involved in the Na+ and/or Cl- absorbing mechanism of MR cells.

“…1D). Na + /K + -ATPase was detected by an affinity-purified rabbit polyclonal antibody directed against a synthetic peptide corresponding to part of the highly conserved region of the Na (Katoh et al, 2000). NHE3 was detected by an affinity-purified rabbit polyclonal antibody directed against a synthetic peptide corresponding to part of the carboxyl-terminal region of tilapia NHE3 (TDTKQMNNDQFPPP) (Watanabe et al, 2008).…”

Section: Antibodiesmentioning

confidence: 99%

Evidence for an apical Na–Cl cotransporter involved in ion uptake in a teleost fish

Hiroi

Yasumasu

McCormick

et al. 2008

Self Cite

245

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