Branchial versus intestinal zinc uptake in wild yellow perch (Perca flavescens) from reference and metal-contaminated aquatic ecosystems

Abstract

Zinc is an essential micronutrient for freshwater fish but can be toxic to them at elevated concentrations. Therefore, the regulation of zinc uptake is important in maintaining homeostasis when fish are chronically exposed to elevated zinc in nature. This study examined the kinetics of in vivo branchial and in vitro intestinal zinc uptake in wild yellow perch (Perca flavescens) from metal-contaminated and reference lakes in northern Ontario. The results showed that the branchial zinc uptake involves high-affinity transport sites, whereas the intestinal zinc uptake involves low-affinity transport sites. Interestingly, significant alterations in the branchial zinc uptake (reduced affinity, increased maximum transport rate) but no apparent changes in the intestinal zinc uptake characteristics were observed in the metal-impacted yellow perch population relative to the reference population. Subsequently, no differences in zinc concentrations of gill, liver, and whole body were recorded between reference and metal-impacted yellow perch populations. Overall, our study indicated that the gill, not the gut, likely plays a critical role in maintaining the zinc homeostasis in wild fish under chronic exposure.