In vitro characterization of calcium transport along the gastrointestinal tract of freshwater rainbow trout Oncorhynchus mykiss.

Using an in vitro gut-sac technique, this study examined the mechanisms of calcium (Ca) uptake along the gastrointestinal tract (GIT) of rainbow trout Oncorhynchus mykiss. Ca uptake into three different compartments (mucous-bound, mucosal epithelium and blood space) of four distinct GIT segments (stomach, anterior intestine, mid intestine and posterior intestine) was monitored after luminal exposure to 10 mM Ca saline (radiolabelled with (45) Ca). Ca transport was determined to be both time-dependent and concentration-dependent. The concentration-dependent kinetics of Ca uptake was investigated using varying luminal concentrations of Ca (1, 10, 30, 60 and 100 mM). In the blood-space compartment, Ca uptake was saturable at high Ca concentrations in the mid intestine (suggesting mediated transport), while linear uptake was found in the other gut segments. In the mucous-bound and mucosal epithelium compartments, however, saturation kinetics were found for most GIT segments, also suggesting mediated transport. Manipulation of serosal saline osmotic pressure with mannitol demonstrated that Ca uptake was not greatly affected by solvent drag. Elevated mucosal cadmium (Cd) did not appear to inhibit Ca uptake into the blood space in any of the GIT sections, and Ca uptake did not appear to be sodium dependent. Maximum transport capacities for Ca and Cd were found to be comparable between the gills and gut, but affinities were much higher at the gills (up to 3000 times).

Branchial cadmium and copper binding and intestinal cadmium uptake in wild yellow perch (Perca flavescens) from clean and metal-contaminated lakes.

Branchial binding kinetics and gastro-intestinal uptake of copper and cadmium where examined in yellow perch (Perca flavescens) from a metal-contaminated lake (Hannah Lake, Sudbury, Ontario, Canada) and an uncontaminated lake (James Lake, North Bay, Ontario, Canada). An in vivo approach was taken for gill binding comparisons while an in vitro gut binding assay was employed for gastro-intestinal tract (GIT) uptake analysis. By investigating metal uptake at the gill and the gut we cover the two main routes of metal entry into fish. Comparisons of water and sediment chemistries, metal burdens in benthic invertebrate, and metal burdens in the livers of perch from the two study lakes clearly show that yellow perch from Hannah L. are chronically exposed to a highly metal-contaminated environment compared to a reference lake. We found that metal-contaminated yellow perch showed no significant difference in gill Cd binding compared to reference fish, but they did show significant decreases in new Cd binding and absorption in their GITs. The results show that gill Cd binding may involve low-capacity, high-affinity binding sites, while gastro-intestinal Cd uptake involves binding sites that are high-capacity, low-affinity. From this we infer that Cd may be more critically controlled at the gut rather than gills. Significant differences in branchial Cu binding (increased binding) were observed in metal-contaminated yellow perch. We suggest that chronic waterborne exposure to Cu (and/or other metals) may be the dominant influence in gill Cu binding rather than chronic exposure to high Cu diets. We give supporting evidence that Cd is taken up in the GIT, at least in part, by a similar pathway as Ca(2+), principally that elevated dietary Ca(2+) reduces Cd binding and uptake. Overall our study reveals that metal pre-exposure via water and diet can alter uptake kinetics of Cu and Cd at the gill and/or the gut.

Bioaccumulation of pharmaceuticals and personal care products in the unionid mussel Lasmigona costata in a river receiving wastewater effluent.

Freshwater mussels are frequently found in rivers receiving effluent from wastewater treatment plants (WWTP), and there is strong evidence that poor water quality is deleterious to freshwater mussel populations. WWTPs are among the main sources of pharmaceuticals and personal care products (PPCPs) in surface waters. We monitored 145 PPCPs in wild and caged mussels both upstream and downstream of the Kitchener WWTP in the Grand River, Ontario, as well as 118 PPCPs in water samples. Our objectives were to characterize the seasonal changes in PPCP concentrations in water, to calculate bioaccumulation factors (BAFs) of PPCPs in mussels, and to determine the chemical and physical properties of PPCPs driving the bioaccumulation. Seventy PPCPs were detected in water, and concentrations were highest in the summer or early fall, which corresponded to low river flow. Forty-three PPCPs from many pharmaceutical classes were detected in mussel tissues, including stimulants, a contrasting agent, anti-inflammatory drugs, anti-bacterial agents, antibiotics, antidepressants, antihistamines, progestins, and illicit drugs such as cocaine and amphetamines. The BAFs ranged from 0.66 for metformin to 32,022 for sertraline. Using partial least squares to predict BAFs based upon chemical properties, log KOC, Log KOW, and fugacity ratio (sediment) all had similar and positive loadings with BAFs (R(2)X = 0.70; caged mussels). BAFs of PPCPs in mussels were predictable from fugacity models that estimate bioconcentration factors using log KOW. Our study demonstrated that mussels readily bioaccumulate PPCPs, in a manner consistent with expectations based upon BCF models and the chemical characteristics of each compound.