Proteomic responses in the gills of fathead minnows (Pimephales promelas, Rafinesque, 1820) after 6 months and 2 years of continuous exposure to environmentally relevant dietary 226Ra

Purpose: To investigate changes in the gill proteome of fathead minnows continually fed an environmentally relevant dietary dose of Ra-226 for 2 years. Methods: The fish were fed a commercial diet containing 10 mBq-10 Bq Ra-226 g(-1). After 6 months and 2 years the gill proteome was analyzed by two-dimensional electrophoresis (2-DE). Protein spots which exhibited a significant change were identified using mass spectrometry. Results: Six proteins were found to be increased: Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), enolase, protein disulphide isomerase precursor, ATP synthase, glial cell fibrillary protein (GFAP), apolipoprotein A1 (ApoA1). One protein was found to be decreased; malate dehydrogenase. The majority of these changes occurred predominantly at the lowest Ra-226 doses, within 6 months and were maintained for 2 years. Conclusions: These proteomic changes suggested an adaptive or protective response to radiation induced reactive oxygen species (ROS). Increased GFAP indicated the induction of oxidative stress. Increased GAPDH and enolase indicated enhanced ROS scavenging from glycolytic metabolites. Increased protein disulphide isomerase precursor indicated an enhanced source of radioprotective thiols. Decreased malate dehydrogenase indicated enhanced ROS scavenging within the mitochondria. Increased ATP synthase indicated enhanced protection of healthy cells and increased ApoA1 indicated enhanced protection of the gill lamellae.