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 the Japanese 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 to hormone treatment by increased immunoreactivity; both staining area and intensity were enhanced with ongoing gonadal development. Moreover, cytoplasmic vacuoles increased in number during artificial maturation, occupying large areas inside hepatocytes. The unusual appearance of hepatocytes may reflect the effect of artificial maturation.

Lipid content and fatty acid composition of muscle, liver, ovary and eggs of captive-reared and wild silver Japanese eel Anguilla japonica during artificial maturation

“…The results in the present study suggest that the transportation of lipids to the liver, possibly from lipid stored in muscle, was induced by SPH injections and continued throughout artificial maturation. This suggestion is supported by histological observations in a previous study; the number and size of oil droplets in the liver were increased during artificial maturation 22 . The previous study also reported that the cytoplasm of hepatocytes was filled with large oil droplets and showed abnormal structures in late stages of maturation 22 .…”

“…This suggestion is supported by histological observations in a previous study; the number and size of oil droplets in the liver were increased during artificial maturation 22 . The previous study also reported that the cytoplasm of hepatocytes was filled with large oil droplets and showed abnormal structures in late stages of maturation 22 . This might be caused by excessive lipid supply from muscle as a result of SPH injections.…”

“…Several reports suggested that after SPH injection, oil droplets in oocytes were immediately increased in both number and size, while yolk globules began to increase later 23,24 . Moreover, it was reported that the serum vitellogenin levels and vitellogenin transcripts were gradually increased after SPH injection and peaked at the migratory nucleus stage 22,25 . These observations suggest that most of the lipids transported to eggs during early maturation were not derived from vitellogenin.…”

Ovarian steroidogenesis and the role of sex steroid hormones on ovarian growth and maturation of the Japanese eel

“…Therefore, the Japanese eel provides an excellent model for studying the regulation of steroidogenesis and function of sex steroid hormones in gametogenesis because the gonadotropic effects of exogenous hormones can be readily assessed. Herein, we sum- were demonstrated to correlate well with the serum levels of E2 [6] and Vtg [10]. These findings suggest that SP-induced E2 regulates Vtg production at the transcriptional level.…”

Structural and expression analysis of hepatic vitellogenin gene during ovarian maturation in Anguilla japonica

“…However, Northern blot analysis barely detected that Vtg expression in the liver following 4 and 12 weeks, respectively, of induction. Numerous eel studies [40][41][42] have demonstrated that serum Vtg levels, using a specific antiserum against Vtg, increased in the early Vtg stage and was reduced in the mid and late Vtg stage during SPH treatment. Conversely, Okumura et al [32] demonstrated that the expression of Vtg in the Japanese eel increased during SPH treatment during the early Vtg to the late Vtg stage and decreased in the migratory nucleus stage.…”