Plasma levels of vitellogenin and eggshell zona radiata proteins in 4-nonylphenol and o,p′-DDT treated juvenile Atlantic salmon (Salmo salar)

Induction of vitellogenin (Vtg) in males and juveniles of oviparous vertebrates has been used as a biomarker for xenoestrogens. Recently, we have demonstrated that synthesis of eggshell zona radiata proteins (Zrp) or zonagenesis is an integral aspect of fish oogenesis (Oppen-Berntsen et al. (1994) Journal of Experimental Zoology 268, 59–70), and that Zrp synthesis is a sensitive biomarker for nonylphenol (Arukwe et al. (1997) Environmental Health Perspective 105, 418–422). This study compares the responses of Vtg and Zrp in plasma of juvenile Atlantic salmon (Salmo salar) treated with 4-nonylphenol (NP) and o,p′-DDT (both at 25 mg kg−1, singly and in combination). Validated ELISA and immunoblot analysis show that Vtg and Zrp respond significantly stronger to NP treatment alone and in combination with o,p′-DDT compared to control and o,p′-DDT treatment alone. However, a slight reduction in NP-induced Zrp levels was indicated when NP was injected in combination with o,p′-DDT.