In situ analysis of cadmium uptake in four sections of the gastro-intestinal tract of rainbow trout (Oncorhynchus mykiss)

This study links results from past in vitro and in vivo experiments, by implementing an in situ experiment in order to determine the relative importance for cadmium (Cd) uptake of different sections of the gastro-intestinal tract (GIT) of rainbow trout. Transport of Cd from four sections of the GIT of adult rainbow trout (∼220 g) was individually examined by infusing ligated sections of the GIT in live, free-swimming fish with 50 μM Cd spiked with radiolabelled 109Cd (0.5 μCi ml−1). Fish were exposed for an 8-h period. The percentage of the total injected 109Cd which was internalized from the different segments was only between ∼0.1 and ∼7%, indicating low uptake efficiency. The stomach is the most important GIT segment for Cd transport into the internal compartment of the animal, while the posterior intestine also plays a significant role. The majority of 109Cd recovered at the end of the flux period was detected within gut material (ranging from 28 to 95%); the portion of Cd which was internalized was largely found in the carcass (32 to 60%). Distribution between the measured organs varied with uptake from the various GIT sections. Our results also confirm that the GIT acts as a protective barrier against Cd uptake from dietary exposure.

► We perform an in situ experiment on the gut of rainbow trout. ► The primary site of Cd uptake along the gut of trout is the stomach. ► Most internalized Cd is found within the carcass. ► The gut acts as a protective barrier against Cd uptake.