1994/05/15 by Marie‐France Sire, Patrick J. Babin, Jean‐Marie Vernier · 1 citation
Agricultural and Biological Sciences · Biochemistry, Genetics and Molecular Biology · Medicine · #Aquaculture Nutrition and Growth #Reproductive biology and impacts on aquatic species #Sperm and Testicular Function
paper · doi:10.1002/jez.1402690109
crossref issued 1994/05/15 · crossref published 1994/05/15 · crossref published-print 1994/05/15 · openalex publication_date 1994/05/15 · crossref published-online 2005/06/07 · crossref created 2005/06/12 · crossref deposited 2023/10/25 · openalex created_date 2025/10/10 · crossref indexed 2026/07/29 · openalex updated_date 2026/07/29
Abstract In adult female rainbow trout ( Oncorhynchus mykiss ), an immunocytochemical study of the oocyte has shown that a proteolytic enzyme, cathepsin D, is localized in multivesicular bodies (MVB) which begin to differentiate before the phase of vitellogenesis. Estrogens cause the liver to synthesize the protein vitellogenin (VTG), which then enters the systemic circulation. During vitellogenesis, endocytosed VTG is co‐localized with cathepsin D in the MVB. Assays of oocyte cathepsin activities have shown that the only proteolytic activity of note is that of cathepsin D. Along with the yolk proteins derived from VTG, this enzyme will be included in the central coalescent yolk mass. With the installation of the yolk syncytial layer and the surrounding yolk vascular system, embryonic development is characterized by high lysosomal activity, especially in the syncytial layer. At this level, proteolytic activity concerns a cathepsin L, secreted as a proenzyme. We propose the hypothesis that cathepsin D, along with the yolk proteins in the yolk globules that break away from the yolk mass in the vitellolysis zone, activates the proenzyme and leads to protein degradation, which then becomes very rapid. © Wiley‐Liss, Inc.