A novel guanylin family (guanylin, uroguanylin, and renoguanylin) in eels: possible osmoregulatory hormones in intestine and kidney.
As the intestine is an essential organ for fish osmoregulation, the intestinal hormone guanylins may perform major functions, especially in euryhaline fish such as eels and salmonids. From the intestine of an eel, we identified cDNAs encoding three distinct guanylin-like peptides. Based on the sequence of mature peptide and sites of production, we named them guanylin, uroguanylin, and renoguanylin. Renoguanylin is a novel peptide that possesses the characteristics of both guanylin and uroguanylin and was abundantly expressed in the kidney. By immunohistochemistry, guanylin was localized exclusively in goblet cells, but not enterochromaffin cells, of the intestine. After transfer of eels from fresh water to seawater, mRNA expression of guanylin and uroguanylin did not change for 3 h, but it increased after 24 h. The increase was profound (2-6-fold) after adaptation to seawater. The expression of uroguanylin was also up-regulated in the kidney of seawater-adapted eels, but that of renoguanylin was not so prominent as other guanylins in both intestine and kidney. Collectively, the novel eel guanylin family appears to have important functions for seawater adaptation, particularly long-term adaptation. Eel guanylin may be secreted from goblet cells into the lumen with mucus in response to increased luminal osmolality and act on the epithelium to regulate water and salt absorption.
Yuge
Shinya
S
Ocean Research Institute, The University of Tokyo, Nakano, Tokyo 164-8639, Japan. yuge@ori.u-tokyo.ac.jp
Inoue
Koji
K
Hyodo
Susumu
S
Takei
Yoshio
Y
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D018076:DNA, Complementary; D004524:Eels / Q000502:physiology*; D005768:Gastrointestinal Hormones / Q000737:chemistry* / Q000235:genetics*; D006801:Humans; D007422:Intestines / Q000502:physiology; D007668:Kidney / Q000502:physiology; D008969:Molecular Sequence Data; D045265:Natriuretic Peptides; D009893:Opossums; D009928:Organ Specificity; D036361:Peptide Hormones / Q000737:chemistry* / Q000235:genetics*; D010455:Peptides / Q000737:chemistry* / Q000235:genetics*; D011994:Recombinant Proteins / Q000737:chemistry; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013552:Swine; D014882:Water-Electrolyte Balance
D017931:DNA Primers; D018076:DNA, Complementary; D005768:Gastrointestinal Hormones; D045265:Natriuretic Peptides; D036361:Peptide Hormones; D010455:Peptides; D011994:Recombinant Proteins; C072685:guanylin; C084362:uroguanylin