Total Zn Levels Research Articles

Effect of the physicochemical properties of zinc oxide sources on their bioavailability in broilers

ABSTRACT 1. The bioavailability of a trace mineral source is related to its intestinal solubility (bioaccessibility), which in turn is determined by its physicochemical properties. It is still not clear which characteristics are more relevant in affecting solubility and bioavailability of mineral sources. Zinc oxide (ZnO) is a common feed additive used to supplement zinc in the diet of monogastric animals. However, different sources have shown variable responses on animal bioavailability. 2. This study hypothesised that different sources of feed grade ZnO have various physicochemical features that lead to distinct bioavailability values. Feed grade ZnO samples collected from the feed industry worldwide were characterised for their physicochemical features and tested in broilers to allow bioavailability determined. 3. A total of 135 male Cobb broiler chickens were fed a standard starter diet from day 1 after hatching up to d 7. At d 8, animals were allocated in individual cages and fed one of the following dietary treatments during 15 days: a basal diet with 23.5 ppm of zinc and seven test diets with supplemented ZnO or zinc sulphate (ZnSO4) at 6 or 12 ppm. 4. Different sources of ZnO showed an effect of solubility in the stomach and supplementation influenced total Zn levels in the ileum. The bioavailability of the different sources varied from 49% to 160% in relation to ZnSO4. Aggregate size of particles seems to explain most of the variability in the bioavailability of the different sources tested in broilers. In conclusion, physicochemical properties of ZnO can partly explain the variability observed in terms of biological value.

Zinc fractionation in cow, goat, sheep and soybean milk samples using gel-electrophoresis and determination by electrothermal atomic absorption spectrometry (ETAAS)

A screening method for zinc levels in different milk samples (raw cow, raw sheep, UHT cow, UHT goat and soybean milk base) was performed to establish the Zn levels’ differences in protein samples. The samples were digested in a cavity microwave oven and the total Zn levels in the extracts were determined by flame absorption atomic spectrometry (FAAS). The protein separation was performed by urea polyacrylamide gel electrophoresis (UREA-PAGE). Protein bands were digested in the cavity microwave oven and Zn-protein analysis was further conducted by electrothermal atomic absorption spectrometry (ETAAS). The results showed that Zn is mainly bound to 32 kDa (β-casein) protein (17.0 ± 2.0%) in UHT cow and 24 kDa (α-casein) protein (9.0 ± 0.6%) in raw sheep milk. This method provided quantitative information regarding Zn species present in the protein fractions of the milk samples. The accuracy was evaluated using certified reference material (whole milk powder, NIST 8435) with statistically equivalent concentrations (Student’s t-test) for total Zn and by addition and recovery experiments applied to measure Zn-protein. The recovered values were in the 92-110% range.

Variation in Zn, C, and N isotope ratios in three stream insects

Total Zn concentrations and Zn isotope ratios were measured, using multicollector inductively coupled plasma (ICP)-mass spectrometry (MS), in three species of aquatic insects collected from a stream in Peterborough, Ontario, Canada. Total Zn levels averaged 193 ± 88 μg/g dry weight (dw) in water striders (Heteroptera: Gerridae, Aquarius remigis) and were significantly higher than the concentrations measured in stonefly nymphs (Plecoptera: Perlidae, Acroneuria abnormis) and caddisfly larvae (Trichoptera: Limnephilidae, Pycnopsyche guttifer), i.e., 136 ± 34 μg/g dw and 125 ± 26 μg/g dw, respectively. Average delta values for 66Zn/64Zn in the water striders were approximately 0.7‰ lighter (−1.2‰ ± 1.0‰) and were significantly different than those measured for stoneflies (−0.45‰ ± 0.62‰) and caddisflies (−0.51‰ ± 0.54‰). Nitrogen isotope ratios were significantly different ( P < 0.05) among the three species suggesting differences in trophic positioning. Similar to the Zn isotope ratios, δ 13C values for the water striders (−28.61‰ ± 0.98‰) were significantly different than those of the stoneflies and caddisflies, i.e., −30.75‰ ± 1.33‰ and −30.68‰ ± 1.01‰, respectively. The data suggest that the differences observed in Zn ratios relate to food source for these insects. Similar to their carbon sources, Zn in water striders appears to be primarily of terrestrial origin, and of aquatic origin for the other two species.

Effects of subchronic exposure to zinc nanoparticles on tissue accumulation, serum biochemistry, and histopathological changes in tilapia (Oreochromis niloticus)

Zinc nanoparticles (ZnNPs) are among the least investigated NPs and thus their toxicological effects are not known. In this study, tilapia (Oreochromis niloticus) were exposed to 1 and 10 mg/L suspensions of small size (SS, 40-60 nm) and large size (LS, 80-100 nm) ZnNPs for 14 days under semi-static conditions. Total Zn levels in the intestine, liver, kidney, gill, muscle tissue, and brain were measured. Blood serum glucose (GLU), glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), and lactate dehydrogenase (LDH) were examined to elucidate the physiological disturbances induced by ZnNPs. Organ pathologies were examined for the gills, liver, and kidney to identify injuries associated with exposure. Significant accumulation was observed in the order of intestine, liver, kidney, and gills. Zn levels exhibited time- and concentration-dependent increase in the organs. Accumulation in kidney was also dependent on particle size; NPs SS-ZnNPs were trapped more effectively than LS-ZnNPs. No significant accumulation occurred in the brain (p > 0.05) while Zn levels in muscle tissue increased only marginally (p ≥ 0.05). Significant disturbances were noted in serum GOT and LDH (p < 0.05). The GPT levels fluctuated and were not statistically different from those of controls (p > 0.05). Histopathological tubular deformations and mononuclear cell infiltrations were observed in kidney sections. In addition, an increase in melano-macrophage aggregation intensity was identified on the 7th day in treatments exposed to LS-ZnNPs. Mononuclear cell infiltrations were identified in liver sections for all treatments. Both ZnNPs caused basal hyperplasia in gill sections. Fusions appeared in the gills after the 7th day in fish treated with 10 mg/L suspensions of SS-ZnNPs. In addition, separations in the secondary lamella epithelia were observed. The results indicated that exposure to ZnNPs could lead to disturbances in blood biochemistry and cause histopathological injuries in the tissues of O. niloticus. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1213-1225, 2017.

Responses of hepatic metallothioneins and apoptotic activity in Carassius auratus gibelio witness a release of cobalt and zinc from waterborne nanoscale composites

The main goal of this study was to evaluate the ability of fish Carassius auratus tissues to release cobalt (Co) and zinc (Zn) cations present in the applied Co- and Zn-containing nanoscale composites (NCs). Male fish was subjected to 14day long action of Co- and Zn-NCs, as well as of Co2+ and Zn2+ or polymeric substance (PS) used for the NC preparation and derived from the vinylpyrrolidone. 50μg∙L−1 of Co and 100μg∙L−1 of Zn were applied either as a salt or a nanocomposite. Both Co and Co-NC increased (3.1 and 2.3 times, respectively) concentration of total Co, metallothionein-related Co (3.7 and 6.6 times, respectively) and thiols (by 71 and 95%, respectively), and caspase-3 activity (2.2 and 3.7 times, respectively) in the fish liver. At the same time, Co and Co-NC decreased glutathione level (1.8 and 1.9 times, respectively) and activated vitellogenesis (5.1 and 9.9 times, respectively) in the fish liver. Both Zn and Zn-NC increased markedly concentrations of metallothionein-related Zn (2.4 and 2.9 times, respectively) and Cu (2.8 and 3.2 times, respectively), and decreased metallothionein-related thiol (2.5 and 4.2 times, respectively), oxyradical (by 30.4 and 44.2%, respectively), and caspase-3 (3.0 and 5.3 times, respectively) levels in the fish liver. These peculiarities are common for metal and metal-NC and witness a release of metal from NS in fish organism. The differences in the levels of DNA strand breaks, biotransformation enzymes and total Zn levels in the liver were dependent on the kind of exposure.

Quantification of ZnO Nanoparticle Uptake, Distribution, and Dissolution within Individual Human Macrophages

The usefulness of zinc oxide (ZnO) nanoparticles has led to their wide distribution in consumer products, despite only a limited understanding of how this nanomaterial behaves within biological systems. From a nanotoxicological viewpoint the interaction(s) of ZnO nanoparticles with cells of the immune system is of specific interest, as these nanostructures are readily phagocytosed. In this study, rapid scanning X-ray fluorescence microscopy was used to assay the number ZnO nanoparticles associated with ∼1000 individual THP-1 monocyte-derived human macrophages. These data showed that nanoparticle-treated cells endured a 400% elevation in total Zn levels, 13-fold greater than the increase observed when incubated in the presence of an equitoxic concentration of ZnCl2. Even after excluding the contribution of internalized nanoparticles, Zn levels in nanoparticle treated cells were raised ∼200% above basal levels. As dissolution of ZnO nanoparticles is critical to their cytotoxic response, we utilized a strategy combining ion beam milling, X-ray fluorescence and scanning electron microscopy to directly probe the distribution and composition of ZnO nanoparticles throughout the cellular interior. This study demonstrated that correlative photon and ion beam imaging techniques can provide both high-resolution and statistically powerful information on the biology of metal oxide nanoparticles at the single-cell level. Our approach promises ready application to broader studies of phenomena at the interface of nanotechnology and biology.

Zinc Accumulation in Plant Species Indigenous to a Portuguese Polluted Site

The levels of zinc accumulated by roots, stems, and leaves of two plant species, Rubus ulmifolius and Phragmites australis, indigenous to the banks of a stream in a Portuguese contaminated site were investigated in field conditions. R. ulmifolius, a plant for which studies on phytoremediation potential are scarce, dominated on the right side of the stream, while P. australis proliferated on the other bank. Heterogeneous Zn concentrations were found along the banks of the stream. Zn accumulation in both species occurred mainly in the roots, with poor translocation to the aboveground sections. R. ulmifolius presented Zn levels in the roots ranging from 142 to 563 mg kg(-1), in the stems from 35 to 110 mg kg(-1), and in the leaves from 45 to 91 mg kg(-1), vs. average soil total Zn concentrations varying from 526 to 957 mg kg(-1). P. australis showed Zn concentrations in the roots from 39 to 130 mg kg(-1), in the stems from 31 to 63 mg kg(-1), and in the leaves from 37 to 83 mg kg(-1), for the lower average soil total Zn levels of 138 to 452 mg kg(-1) found on the banks where they proliferated. Positive correlations were found between the soil total, available and extractable Zn fractions, and metal accumulation in the roots and leaves of R. ulmifolius and in the roots and stems of P. australis. The use of R. ulmifolius and P. australis for phytoextraction purposes does not appear as an effective method of metal removing, but these native metal tolerant plant species may be used to reduce the effects of soil contamination, avoiding further Zn transfer to other environmental compartments.

Kinetic analysis of zinc accumulation in the gills of juvenile rainbow trout: Effects of zinc acclimation and implications for biotic ligand modeling

AbstractJuvenile rainbow trout were acclimated to hard water (Ca2+ = 1.0 mM, Mg2+ = 0.2 mM; hardness = 120 mg CaCO3/L) and hard water plus 250 μg/L Zn (3.8 μM). After 30 d of exposure, there was no difference in the total Zn levels of the gills of Zn‐exposed and control fish (˜70 μg Zn/g gill). Exposure of both groups to a range of Zn concentrations (0–2,900 μg/L Zn) for up to 7 d also had no effect on the measured total Zn levels in the gills. However, using radiolabeled 65Zn, measurement of new Zn appearance in the gills was possible. Trout were exposed to a range of Zn concentrations (with 65Zn) and the gills were sampled at times ranging from 0.5 to 72 h. The fast turnover pool of Zn in the gills increased with increasing acute Zn exposure concentration, while the maximum size of the fast pool was about ninefold larger in Zn‐acclimated fish (4.14 μg Zn/g gill) versus control fish (0.45 μg Zn/g gill). At all sampling times, gill 65Zn accumulation exhibited saturation kinetics, allowing calculation of binding capacity (Bmax) and affinity (Kd). In both control and Zn‐acclimated trout, Kd decreased rapidly (affinity increased) from 0.5 to 3 h and then remained constant up to 72 h. Bmax increased rapidly from 0.5 to 3 h in both groups, then the rate of increase began to subside but was still increasing from 24 to 72 h. At all times, the Kd of Zn‐acclimated fish was higher (i.e., lower affinity) and Bmax was greater than controls. The stabilized Kds (&gt;3 h) were approximately 280 μg/L total Zn (log K = 5.6 as Zn2+) and 575 μg/L total Zn (log K = 5.3 as Zn2+) in control and Zn‐acclimated fish, respectively. The Bmax of control fish at 0.5 h was 0.37 μg Zn/g gill and increased to 8.63 μg Zn/g gill by 72 h. The Bmax of Zn‐acclimated fish increased from 0.70 to 11.61 μg Zn/g gill over the same time period. Preexposure to 250 μg/L Zn appeared to have little effect on acute zinc toxicity, though the 96‐h LC50s for both groups were relatively high (˜3,000 μg/L Zn) in comparison to previous measurements. The relationship between gill binding constants for different metals and relative toxicity is critically assessed with respect to biotic ligand modeling.

Oxidative stress induced by copper: defense and damage in the marine planktonic diatom Ditylum brightwellii, grown in continuous cultures with high and low zinc levels

Light-limited cultures of the planktonic diatom Ditylum brightwellii (West) Grunow were grown at 14‰ salinity. Cells were subjected to oxidative stress induced by copper, in the presence of zinc. In two continuous cultures with total Zn levels of 40 and 140 nM, respectively, dissolved Cu levels were increased from 3 to 126 nM. This resulted in an increased Cu adsorption capacity of the cell walls, probably due to an increase of surface area and roughness. Sexual reproduction (auxospore formation) was accelerated but was considered as a non-specific stress response. Cu-induced oxidative stress was indicated by a decrease of reduced glutathione (GSH), and a removal of superoxide anions monitored as an increasing activity of superoxide dismutase (SOD). Although Zn has no oxidative potential per se, cell division rates and chlorophyll c contents were lower in the culture with high Zn levels. In both cultures, the pro-oxidant Cu caused a decrease of chlorophyll a, decreasing photosynthetic O2 evolution and cell devision rates, and a growing number of deformed and broken cells.

Effects of Zinc on Rat Hepatoma HTC Cells and Primary Cultured Rat Hepatocytes

Responses to zinc, applied in concentrations ranging from 3 to 200 μM Zn 2+, were investigated in rat hepatoma tissue culture (HTC) cells and in primary cultured rat hepatocytes. The uptake of 65Zn, total Zn levels, cellular viability, metallothionein (MT) levels, superoxide dismutase (SOD) activities, and glutathione (GSH) levels were measured. Exposure at 50-200 μM Zn for 24 hr resulted in up to fivefold increases in intracellular Zn accumulation in hepatocytes and up to twofold increases in rat HTC cells. Hepatocytes increased their MT levels from 80 to 230 pmol MT/mg cell protein, whereas MT levels in HTC cells did not significantly change with increasing Zn applications. SOD activities rapidly increased in both cell types for applied [Zn] < 25 μM, eventually reaching up to two to three times the control SOD values at 200 pM applied Zn concentrations. GSH levels in hepatocytes increased to twice the control values, but gradually declined again with applied Zn concentrations < 100 pM, the latter probably due to progressive increases in GSH efflux. Cell viability tests indicated differences between effects on cellular metabolism (ATP levels) and effects on cellular condition (LDH leakage, 42K influx). The ATP data suggest significant but comparable Zn effects on cellular metabolism in both cell types, notwithstanding the large differences in cellular Zn, MT. and GSH levels. At comparable cytosolic total Zn levels, hepatocytes appeared more effectively protected against intracellular Zn toxicity by elevated MT and GSH levels. However, if considered with respect to applied Zn concentrations, at 200 μM cellular viability (LDH leakage) was more affected in hepatocytes than in HTC cells, the latter probably due to progressive sequestering of zinc on intracellular Zn-complexing compounds (MT, GSH) and subsequent accumulation of zinc in hepatocytes, in contrast with the absence of excessive Zn uptake by HTC cells. The overall results indicate that synthesis of (protective) cellular compounds like MT or GSH, although rendering cells resistant to metals, may-at the same time-result in relatively strong accumulation of potentially toxic metals.

The effect of sewage sludge application to bermudagrass on forage quality production, and metal accumulation

A bermudagrass ( Cynodon dactylon (L.) Pers. cv. ‘Alicia’) sod was top-dressed with nutrient rates of 0-0-0, 180-78-20, 360-156-40 and 540-234-60 kg ha −1 N, P and K, respectively, from commercial fertilizer and dried anaerobically digested sewage sludge. Mean seasonal dry matter production was similar regardless of nutrient source, but higher rates generally resulted in significantly higher yields. Treatment of forage with sludge rather than commercial fertilizer gave a higher crude protein content only at the 360-156-40 rate. In vitro dry matter digestibility was significantly lower at the medium and high sludge rates. All other treatments were not significantly different. Total Zn levels in forage from all sludge treatments were relatively uniform. Cr concentration was highest in the medium sludge rate and was lowest with the highest rate of commercial fertilizer among plots treated with supplemental nutrients. Hg concentration did not vary with nutrient source. Cu concentrations were generally twice as high in sludge-treated compared to conventionally fertilized forage. In no case did the metal concentration pose a threat to grazing animals.

Trenching of Digested Sludge

Effects of trenching digested sludge were evaluated for 4 yr. Digested sludge buried in trenches that were 2 ft (0.6m) wide by 2 ft (0.6m) deep and 2 ft (0.6m) apart was sampled along with the surrounding soil and analyzed for N, Cl, and heavy metals. Most of the Cl leached into the profile during the first 2 yr. After 4 yr, nearly all the Cl leached from the sludge and surrounding soil profile. More N leached from the sludge in the first 2 yr than the second 2 yr. After 4 yr, the sludge was nearly stabilized as judged from its mineralization rate. Zinc was the only heavy metal found in detectable levels in the soil profile beneath the trenches. The amount of Zn leached was minor as compared with the total Zn levels in the entrenched sludge.