Molecular characterization and gene expression of Japanese eel (Anguilla japonica) gonadotropin receptors.

A luteinizing hormone receptor (lhr) cDNA with high identity to other fish lhrs was fully cloned from the ovary of the Japanese eel (Anguilla japonica). The genes for two gonadotropin receptors (Gthr), follicle-stimulating hormone receptor (fshr) and lhr, were differentially expressed during oogenesis, which was artificially induced by salmon pituitary extract, a gonadotropin-rich source. Transcript abundance of fshr was significantly elevated at the early vitellogenic stage and peaked at the late vitellogenic stage, while lhr gene expression rapidly induced at the late vitellogenic stage and thereafter remained at a high level.