Effects of dietary selenomethionine on larval rainbow trout (Oncorhynchus mykiss).

Increased selenium (Se) concentrations in water (>10 microg/L) have been measured in the San Diego Creek, which is a tributary of the Upper Newport Bay in Orange County, CA. The objective of this study was to develop tissue- and dietary-based thresholds for Se in resident fish species in San Diego Creek. A 90-day dietary experiment was conducted to determine the effects of seleno-L-methionine (SeMe) on the growth, survival, and whole-body Se accumulation in larval (24-day-old) rainbow trout. Decreased and oxidized glutathione (GSH-to-GSSG ratio) and thiobarbituric acid-reactive substances (TBARS) were also measured in livers of exposed animals to assess oxidative damage caused by Se. Fish food was spiked with SeMe to contain 4.6, 12, and 18 microg/g (dry weight) of Se. Fish exposed to SeMe for 90 days exhibited a significant decrease in body weight and fork length in the 4.6 and 12 microg/g Se treatments compared with controls. Whole-body total Se concentrations increased significantly in fish fed 12 and 18 microg/g SeMe after 90 days compared with controls. Lipid peroxidation (TBARS) and GSH-to-GSSG ratios were unchanged by SeMe treatment. Based on decreased growth after 90 days, a dietary Se lowest observed-effect concentration (LOEC) value of 4.6 microg/g and a Se body burden LOEC of 1.20 microg/g (wet weight) were estimated.