1Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido 041-8611, 2Hokkaido National Fisheries Research Institute, Fisheries Research Agency, Kushiro, Hokkaido 085-0802, 3South Ehime Fisheries Research Center, Ehime University, Ainan, Ehime 798-4131, 4Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido 041-8611, Japan
Two types of vitellogenin cDNA (vtgAs and vtgC) were cloned from the liver of cutthroat trout. Quantification of hepatic expression levels of vtg transcripts revealed that both vtg mRNA levels showed strong positive correlations with gonad somatic index (GSI). Quantification of serum levels of Vtg proteins revealed that these levels also showed positive, albeit weak, correlations with GSI; however, Vtg levels seemed to be maintained at high but constant levels in individuals with high GSI (i.e., greater than 2). This is the first report on changes associated with ovarian growth in levels of dual vtg/Vtg sub-types within single salmonidae species, providing a basis for a dual vtg/Vtg model in this group of fish.