Comparison of protein expression in plasma from nonylphenol and bisphenol A-exposed Atlantic cod (Gadus morhua) and turbot (Scophthalmus maximus) by use of SELDI-TOF

The overall objective of this study was to compare the expression of plasma proteins in juvenile cod and turbot after a 3 week exposure to two different chemicals known to be estrogenic: 4-nonylphenol (NP, 29 μg/L) and bisphenol A (BPA, 59 μg/L). ProteinChip® array technology in combination with surfaced enhanced laser desorption ionisation-time of flight (SELDI-TOF) was used to investigate general responses in plasma proteins. In addition, an indirect enzyme-linked immunosorbent assay (ELISA) was used to analyse two specific biomarkers of estrogenic exposure, vitellogenin (Vtg) and zona radiata protein (Zrp) in plasma. Both methods revealed clear species specific responses. In cod, 67% of significantly altered proteins showed the same response (up or down regulated) in NP and BPA exposed animals (males and females combined). The rest were either specific to NP (10%), BPA (19%) or they showed opposite responses to the two chemicals (4%). In contrast, only 20% of significantly altered proteins were common for NP and BPA exposed turbot: 60% were altered only in NP and 17% only in BPA. Furthermore, in BPA exposed cod, 77% of the responses were common for male and females, whereas turbot showed only 21% similarity for the two genders. However, NP exposed male and female turbot showed 88% similarity in responses. As gender was not determined in NP exposed cod, gender specific responses could not be determined. ELISA results supported that cod responded clearly to both chemicals as a large increase was observed in Vtg and Zrp levels. Turbot responded strongly to NP, but seemed only slightly affected by BPA. Overall, the results indicated that cod are more sensitive or respond with less specificity to estrogenic chemicals than turbot. The relatively large degree of common responses in NP and BPA exposed cod may indicate that in cod BPA have similar mode of action as NP. Generally, the results show the potential of SELDI-TOF as a tool for comparing multiple responses, and for identifying exposure as well as gender specific responses.