Purification and identification of vitellogenin and its immunohistochemical detection in growing oocytes of the teleost,Oryzias latipes

“Probable vitellogenin” [Hamazaki et al. (1985) J. Exp. Zool., 235:269–279] of the medaka, Oryzias latipes, was purified from the ascites of estrogen-fed (EF) fish and was identified as the real vitellogenin by examining some of its biochemical characteristics. It has an amino acid composition and phosphorus content (0.8%) quite similar to those of the vitellogenin of rainbow trout and goldfish. The molecular weight (mw) in the native state was about 420,000, but sodium dodecyl sulfate denaturation produced a group of peptides that included a major peptide of about 200,000 mw with an isoelectric point of 3.8–4.0. Immunohistochemical observations with the use of the anti-vitello-genin antibody raised against the purified vitellogenin as a probe indicated that a considerable immunoreactivity appeared in some vesicles of the oocytes at the yolk-vesicle stage (ca, 150–250 μm in diameter). However, yolk deposition in the oocytes seemed to occur at the later stage (vitellogenic stage, over 300 μm in diameter) as judged from histological examination of the the hematoxylin-stained materials. Moreover, the immunofluorescence was observed in the intercellular spaces among the follicle cells of the vitellogenic oocyte. The observation indicates that the pathway of vitellogenin transportation through the follicle cell layer into the oocyte is present in the extracellular matrix of the follicular epithelium.