Salmon eggshell protein expression: A marker for environmental estrogens

A liver complementary DNA expression library from Atlantic salmon (Sa lmo salar) pretreated with estradiol-17 beta (E-2) was constructed an d screened with antibodies raised against salmon eggshell (zona radia ta) proteins. Two clones, SalZr2_19 and SalZr2_23 were sequenced and shown to encode proteins of approximately 50 kDa. SalZr2_23 contains 12 octamer Sequence LPQR/KPA/VQ repeats also found in SalZr2_19, but only twice. Alignment reveals that the two salmon sequences are simil ar to piscine zona radiate proteins and mammalian zona pellucida prot eins. Several transcripts ranging from 2.3 to 12 kb appeared in liver extracts of E-2-treated fish. Juvenile fish treated with E-2 or 4-no nylphenol showed strong induction of zona radiata protein. The use of egg envelope transcriptional and translational induction in male or juvenile fish as a biological marker of environmental estrogens is di scussed.