Changes in serum vitellogenin levels and immunohistochemical localization of vitellogenin in hepatic cells during ovarian development in the Japanese eel

ABSTRACT: The present study was designed to quantify changes in serum vitellogenin (VTG)levels and to localize VTG in hepatic cells immunohistochemically during artificial maturation of theJapanese eel Anguilla japonica . Hormone treatment resulted in a gradual rise in serum VTG levels,in which the highest values were attained at the migratory nucleus stage. Hepatocytes responded tohormone treatment by increased immunoreactivity; both staining area and intensity were enhancedwith ongoing gonadal development. Moreover, cytoplasmic vacuoles increased in number during arti-ficial maturation, occupying large areas inside hepatocytes. The unusual appearance of hepatocytesmay reflect the effect of artificial maturation. KEY WORDS: Japanese eel, lipovitellin, liver, vitellogenesis, vitellogenin. *Corresponding author: Tel: 81-298-50-2757. Fax: 81-298-50-2233. Email: okumura.hiromi@nasda.go.jp a Present address: Space Utilization Research Program,National Space Development Agency of Japan, Tsukuba, Ibaraki305-8505, Japan.Received 24 October 2000. Accepted 9 February 2001.