Metallothionein in intestine of red mullet, Mullus barbatus as a biomarker of copper exposure in the coastal marine areas

Dietary metal exposure in fish is studied in native red mullet, Mullus barbatus, involving metallothionein (MT) response in the intestine, a primary site for metal uptake. Intestinal MTs (μg mg−1 proteins), total proteins (mg ml−1 S50), Cu, Zn, Fe, Mn and Cd (μg ml−1 S50) are considered as indicators of metal exposure in specimens from near-shore and off-shore locations of the Eastern Adriatic Sea. Metallothionein and Cu are statistically significantly higher in 68 specimens from the Kaštela Bay, a near-shore area (30.0 ± 6.71 μg MT mg−1 proteins; 0.30 ± 0.08 μg Cu ml−1 S50), in comparison to 51 specimens from off-shore area, Šolta Island (25.9 ± 4.21 μg MT mg−1 proteins; 0.26 ± 0.09 μg Cu ml−1 S50). Cytosolic Cu, a MT inducer, is significantly correlated (p < 0.05, r = 0.44) with MT in specimens from the Kaštela Bay, independent on fish biometry. Our study indicates that cytosolic intestinal Cu and MT represent a measurable biochemical response in red mullet specimens, dwelling above sediments contaminated with Cu.