Salmon Eggshell Protein Expression: A Marker for Environmental Estrogens.

: A liver complementary DNA expression library from Atlantic salmon (Salmo salar) pretreated with estradiol-17beta (E2) was constructed and screened with antibodies raised against salmon eggshell (zona radiata) 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 similar to piscine zona radiata proteins and mammalian zona pellucida proteins. Several transcripts ranging from 2.3 to 12 kb appeared in liver extracts of E2-treated fish. Juvenile fish treated with E2 or 4-nonylphenol 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 discussed.