Growth hormone and insulin-like growth factor I of a Euryhaline fish Cottus kazika: cDNA cloning and expression after seawater acclimation.
The four-spine sculpin Cottus kazika is a euryhaline teleost, in which faster growth in seawater (SW) and freshwater (FW) has been reported. In this study, cDNA clones encoding growth hormone (GH) and insulin-like growth factor I (IGF-I) were isolated from this species to examine the involvement of the GH/IGF-I axis in osmotic adaptation. The amino acid sequence of GH predicted from cDNA was highly similar to those of other fish species, 92% to Sparus aurata, 67% to Paralichthys olivaceus, and 63% to Oncorhynchus keta. The predicted sequence of IGF-I was also exhibited high similarity to those of other fishes, 97% to Myxocephalus scorpius, 95% to P. olivaceus, and 81% to O. keta. Tissue distribution of GH and IGF-I mRNA in fish reared in FW and SW was examined by reverse transcription-polymerase chain reaction (RT-PCR). The GH mRNA was detected only in the pituitary gland. The major site of IGF-I mRNA expression was the liver while minor signals were detected in various tissues including the pituitary, gill, fin, heart, spleen, intestine, and kidney. The expression level of GH mRNA in the pituitary was not different between FW- and SW-reared fish. However, the level of IGF-I mRNA in the liver of SW-reared fish was significantly higher than that of FW-reared fish. These results suggest the possible involvement of hepatic IGF-I in SW adaptation of this species.
Inoue
Koji
K
Ocean Research Institute, University of Tokyo, 1-15-1 Minamidai, Nakano, Tokyo 164-8639, Japan. unouek@ori.u-tokyo.ac.jp
Iwatani
Hozi
H
Takei
Yoshio
Y
D000222:Adaptation, Physiological / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001835:Body Weight / Q000502:physiology; D003001:Cloning, Molecular; D017931:DNA Primers; D018076:DNA, Complementary / Q000096:biosynthesis*; D005618:Fresh Water; D005786:Gene Expression Regulation / Q000235:genetics; D006128:Growth / Q000502:physiology; D013006:Growth Hormone / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D008297:Male; D008969:Molecular Sequence Data; D010473:Perciformes / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012623:Seawater; D014018:Tissue Distribution
D017931:DNA Primers; D018076:DNA, Complementary; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone