ELECTROPHORETIC PATTERNS OF YOLK PROTEINS THROUGHOUT OVARIAN DEVELOPMENT AND THEIR RELATIONSHIP TO VITELLOGENIN IN THE RAINBOW-TROUT, ONCORHYNCHUS-MYKISS

1. Electrophoretic patterns of yolk proteins were investigated throughout ovarian development and their relationship to vitellogenin determined in a pulse-chase experiment with H-3-vitellogenin. 2. Using a radioimmunoassay for vitellogenin, vitellogenin/yolk protein products of vitellogenin were detected in follicles throughout ovarian development and in ovulated eggs. 3. The majority of yolk proteins in follicles measuring less than 1.0 mm in diameter appeared to be derived from sources other than vitellogenin. In contrast, in the larger follicles all of the major yolk proteins detected were derived from vitellogenin. 4. Pulse-chase with H-3-vitellogenin revealed that all of the major yolk proteins in 3.0 mm follicles were derived from vitellogenin. The major peptides eluted with molecular masses of 110 and 30 kDa under non-reducing conditions (these are very likely to represent lipovitellin 1 and lipovitellin 2), and 88, 22, 16, and 12 kDa under reducing conditions. 5. There were no apparent differences in the major yolk proteins in ovulated eggs compared to those in vitellogenic follicles, indicating that no extensive proteolysis of these proteins had occurred during maturation and/or ovulation.