Molecular evidence and physiological characterization of iron absorption in isolated enterocytes of rainbow trout ( Oncorhynchus mykiss): Implications for dietary cadmium and lead absorption

• Published in: Aquatic toxicology 2010-09, Vol.99 (3), p.343-350
• Main Authors: Kwong, Raymond W.M., Andrés, Jose A., Niyogi, Som
• Format: Article
• Language: English
• Subjects: Absorption; Agnatha. Pisces; Animal, plant and microbial ecology; Animals; Applied ecology; Biological and medical sciences; Cadmium; Cadmium - chemistry; Cadmium - metabolism; Cadmium - toxicity; Cation Transport Proteins - antagonists & inhibitors; Cation Transport Proteins - genetics; Cation Transport Proteins - metabolism; DMT1; Ecotoxicology, biological effects of pollution; Enterocytes - drug effects; Enterocytes - metabolism; Fish; Fundamental and applied biological sciences. Psychology; General aspects; Interactions; Intestine; Iron; Iron - chemistry; Iron - metabolism; Lead; Lead - chemistry; Lead - metabolism; Lead - toxicity; Oncorhynchus mykiss; Oncorhynchus mykiss - metabolism; RNA, Messenger - metabolism; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; Water Pollutants, Chemical - chemistry; Water Pollutants, Chemical - metabolism; Water Pollutants, Chemical - toxicity
• ISSN: 0166-445X; 1879-1514
• DOI: 10.1016/j.aquatox.2010.05.012

Recent studies suggested the probable involvement of an apical iron (Fe 2+) transporter, the divalent metal transporter-1 (DMT1), in the uptake of several divalent metals in fish. The present study examined the gastrointestinal expression of the DMT1 gene, and investigated the kinetics of Fe 2+ uptake and its interactions with cadmium and lead in isolated enterocytes of freshwater rainbow trout ( Oncorhynchus mykiss). The expressions of two DMT1 isoforms ( Nramp-β and -γ) were recorded along the entire gastrointestinal tract of fish as well as in the enterocytes. Fe 2+ uptake in isolated enterocytes was saturable and sensitive to the proton gradient and membrane potential, suggesting DMT1-mediated transport. Both cadmium and lead inhibited Fe 2+ uptake in isolated enterocytes in a concentration-dependent manner, and lead appeared to be a stronger inhibitor than cadmium. The kinetic characterization of Fe 2+ uptake revealed that the apparent affinity of uptake was significantly decreased (increased K m) in the presence of either cadmium or lead, whereas the maximum uptake rate ( J max) remained unchanged—indicating that the interaction between Fe 2+ and cadmium or lead is competitive in nature. Overall, our study suggests that the uptake of dietary cadmium and lead may occur via the iron-transporting pathway in fish.