Fate of [ 3 H]-Deoxynivalenol in Rainbow Trout ( Oncorhynchus mykiss ) Juveniles: Tissue Distribution and Excretion

Deoxynivalenol (DON), a Fusarium mycotoxin, is one of the most prevalent mycotoxins in aquafeeds. The toxicokinetics of DON are rarely studied in aquatic species. The present study used juvenile rainbow trout (Oncorhynchus mykiss) with a mean initial body weight of 7.72 ± 1.42 g in order to evaluate the pharmacokinetic behaviour and the metabolization of radiolabelled DON ([3H]-DON). In a first trial, 30 fish were tube-fed with four pellets containing a total of 125 ± 0.019 ng of [3H]-DON. At different sampling time points after feeding (1 h, 3 h, 6 h, 12 h or 24 h), the tissue distribution of the [3H]-DON was assessed by liquid scintillation counting. In a second trial, five fish were tube-fed four pellets containing a total of 663 ng of unlabelled-DON. Twenty-four hours after feeding, metabolites of DON excreted into the water were analysed by LC-MS/MS. [3H]-DON was detected in fish liver one hour after tube-feeding, indicating a rapid absorption of DON. In the first hour, [3H]-DON achieved its maximum in the gastro-intestinal tract (GIT) (20.56 ± 8.30 ng). However, 6.19 ± 0.83 ng of [3H]-DON was also detected in the water at this sampling time point. The fast excretion of [3H]-DON (above the average gastric emptying time of trout) might be related to its high-water solubility and consequent excretion with the fluid phase of the chyme. The amount of [3H]-DON in the GIT was stable during the first six hours. Such long transit time of DON through the GIT increases the potential for damage and absorption. The period between six and twelve hours seems to be the turning point in terms of DON excretion. Twelve hours after tube-feeding, the trout excreted 50.71 ± 22.17% of the tube-fed DON amount into water, while at the previous sampling time point (six hours) only 11.03 ± 6.09% were detected. These data suggest that an effective method for gastrointestinal DON detoxification in trout requires a period of action lower than six hours. In the present trial, no DON metabolites were detected in water.