Tissue Zn Levels Research Articles

Relationships between the Partitioning of Trace Metals in Sediments and Their Accumulation in the Tissues of the Freshwater Mollusc Elliptio complanata in a Mining Area

Surficial sediment samples and specimens of a benthic freshwater pelecypod, Elliptio complanata, were collected at eight sites located along a metal contamination gradient downstream from the mining and smelting complex in Rouyn–Noranda, Quebec. The molluscs were dissected, digested, and analysed for Cu, Pb, Zn, Fe, and Mn by flame atomic absorption spectrophotometry. Each sediment sample was wet sieved and the < 70-μm granulometric fraction was subjected to a sequential extraction procedure designed to determine the partitioning of the trace metals among various geochemical phases. Regression analysis indicates that Cu, Pb, and Zn levels in various tissues of E. complanata (or in the whole organism, without the shell) are best related, not to total metal concentrations in the adjacent sediment, but rather to one or more of the relatively easily extracted fractions. Accumulation of Cu, Pb, and Zn was also influenced by the protective or competitive effect of other sediment constituents, notably amorphous iron oxyhydroxides and, to a lesser degree, organic matter.

Trace metal content of live tissues inhalimione portulacoidesfrom coastal areas of the Sado estuary, Portugal

Large differences were noted in Al, Cu. Fe and Zn levels in live tissues of Halimione portulacoides from the coastal areas of the Sado estuary. The higest levels of Al. Cu and Fe were always found in roots, while the lowest levels were always observed in stems. Copper and iron levels were highly correlated in all tissues, specially Cu P > 0.01), while for Al and Zn high correlations were noted between the leaf and the stem P > 0.05).

Zinc Toxicity, Zinc Deficiency and Zinc-Copper Interrelationship in Eimeria acervulina-Infected Chicks

Three experiments were conducted with young chicks to investigate the effect of duodenal coccidiosis caused by Eimeria acervulina infection on Zn toxicity, Zn deficiency and the interrelationship between Zn and Cu. The coccidial infection depressed both rate and efficiency of weight gain. Dietary Zn addition at 2000 mg/kg depressed performance only slightly, but the 4000 mg/kg reduced both gain and gain/feed markedly. The coccidial infection appeared to have an ameliorative effect on Zn toxicity as assessed by performance and by hematological parameters. Excess Zn (2000 and 4000 mg/kg) dramatically increased liver, pancreas and bone Zn levels. The cocidial infection, however, decreased tissue Zn levels. Copper toxicity caused by feeding 500 mg Cu per kilogram diet was exacerbated by E. acervulina infection. A Zn-Cu antagonism was observed in both control and in coccidiosis-infected chicks. Excess dietary Zn decreased tissue Cu deposition, but excess Cu did not affect tissue Zn deposition. Copper partially ameliorated Zn toxicity symptoms. The efficacy of Cu in overcoming the Zn-induced depressed hematological parameters, however, was enhanced slightly by coccidiosis. E. acervulina infection did not affect the chick's Zn requirement. Growth data were more reliable as indicators of the Zn requirement than were blood or bone parameters.

Effects of Dietary Fibers on Mineral Status of Chicks

We investigated the effects of replacing dietary starch with dietary fibers of various types and particle sizes on utilization of bivalent cations by chicks. Inclusion of polyethylene powder, alfalfa cell walls, corn bran, oat bran and wheat bran into diets resulted in lower serum and tibia Zn levels. However, addition of pectin, cellulose and a xylose:gum arabic (50:50) mixture did not affect tissue Zn levels, whereas addition of 4% lignin increased serum Zn level from 2.50 to 3.44 µg/ml. Ingestion of fibers with particle sizes less than 300 µm resulted in higher serum Zn levels compared with those of particle sizes greater than 300 µm. Incorporation of 4 and 8% pectin decreased (P < 0.05) serum and tibia Mg levels. When brans were fed, kidney Mg levels were lower due to fiber additions. Inclusion of lignin, the xylose:gum arabic mixture and alfalfa cell walls resulted in lower liver Cu levels; polyethylene and solka floc had no effect on liver Cu status. Fiber did not affect tissue Ca or Fe status. Each mineral influenced by fiber type, level or particle size appeared to be affected through different mechanisms.

The induced synthesis of metallothionein in various tissues of rats in response to metals. II. Influence of zinc status and specific effect on pancreatic metallothionein

Metallothionein (MT) of various tissues contains bound zinc (Zn) and any change in Zn status can alter its synthesis and tissue deposition. The changes in MT levels and its inducibility in Zn-injected and Zn-deficient (Zn-D) rats were studied. MT levels in 11 tissues (brain, lung, heart, liver, kidney, stomach, small intestine, pancreas, spleen, testes and muscle) of control and rats injected with different doses of ZnSO 4 (20 mg Zn/kg for 2, 4 or 7 times) were measured by the cadmium-hemolysate (Cd-hem) method. A dose dependent increase in MT levels was observed only in the pancreas, liver, small intestine and kidney after ZnSO 4 injection — the highest level being in the pancreas. A positive correlation was found between Zn and MT concentrations and also the relative inducibility of MT was similar in these 4 tissues (slopes of regression equations were 12.6–15.5). In order to study the effect of Zn-D in MT induction, rats were fed a diet containing 1 ppm Zn for 18 days and CdCl 2 (1 mg Cd/kg) was injected subcutaneously 3 times at 48-h intervals to control and Zn-D rats. Although the tissue distribution of Cd was similar in both the groups, MT concentrations in pancreas and kidney were significantly decreased in Zn-D. The plasma and tissue levels of Zn were also decreased in Zn-D rats injected with CdCl 2. The decrease in both Zn and MT levels was more prominent in pancreas than other organs of Zn-D rats. The results suggest that of all the organs studied, the induction of pancreatic MT is sensitive to Zn status and Zn may be a primary inducer of MT.

Tissue Fe/Zn ratio as a diagnostic tool for prediction of Zn deficiency in crop plants

Critical Zn levels in tissues currently used for the prediction of Zn deficiency in crop plants often fail to explain the anomaly of diminished yield levels in spite of the higher tissue Zn levels, much above the critical Zn levels in crop plants. The study on tissue Zn content, Fe content and tissue Fe/Zn ratios in maize (at the time of appearance of deficiency symptoms-25 day old plants) reveals that the tissue Fe/Zn ratio appears to be a promising diagnostic tool for the prediction of Zn deficiency in crop plants. It also explains the phenomenon of diminished yield levels associated with the high Zn levels often much above the critical Zn levels in crop plants. Correlations between dry matter yields and tissue Fe/Zn ratios were found to be negative and significant. This shows that the yield diminishes as the tissue Fe/Zn ratio increases beyond a certain critical Fe/Zn ratio. Relative per cent yields against the tissue Fe/Zn ratios were plotted using the approach of Cate and Nelson2 which shows that there is a certain critical Fe/Zn ratio in crop plants beyond which there is a hidden Zn deficiency and a probable response to Zn application. Critical Fe/Zn ratio in maize was found to be around 6.0.

425 EFFECTS OF TESTOSTERONE ON ZINC METABOLISM IN RATS

We have measured Zinc (Zn) levels in different tissues of castrated rats (CR) fed purified diet containing 100 pp Zn for 6 wks with and without injection of testosterone (T) enanthate (20 mg IM) 2 wks prior to sacrifice. CR had very low serum T (0.6 ± 0.1 ng/ml) as compared with the controls (8.2 ± 0.7 ng/ml) and T administration restored serum T to normal levels (9.1 ± 1.1 ng/ml).After castration, serum and tissue Zn levels were significantly decreased with concomitant increase in urinary Zn (see Table). Administration of T to CR increased the serum and tissue Zn levels almost to the normal level. Since food intake was similar in all groups, T in CR may have increased Zn retention. These results strongly suggest a positive relationship between Zn and T metabolism.

The effect of Pb and Cd uptake on Zn and Cu levels in hard and soft tissues of rats†

Male Wistar rats received a combination of 25 ppm PbCl2 and 5 ppm CdCl2 in drinking water at different developmental stages. Zn and Cu levels of incisors, molars, epiphyses, diaphyses and kidney cortex were recorded by atomic absorption spectrophotometry. Pb‐Cd uptake in rats, either via the mother through placenta or mammae, or directly in growing rats resulted in an overall decrease in Zn content of epiphyses. This may cause a decreased growth rate. There was a significant negative correlation between Pb and Zn in epiphyses. In addition, an increase in the Zn level of kidney cortex was found in the animals receiving Pb‐Cd from weaning until sacrifice, and through all stages there was a significant positive correlation between Zn and Cu in this tissue. Pb‐Cd administration during pregnancy and/or lactation resulted in an increased storage of Cu in hard as well as soft tissues of the offspring. This storage did not take place if Pb‐Cd were given after termination of the lactation period. There was a posit...

The disposition of cadmium and zinc inPandalus montagui

Cadmium uptake rates in various tissues of Pandalus montagui exposed to sea water containing 37 micrograms Cd/L for 14 days ranged from 0.002-0.06 microgram/dry tissue/hr. During depuration for 57 days, the levels in most tissues decreased slightly, but continued to rise in the hepatopancreas indicating Cd redistribution. Exposure to 65 micrograms Zn/L produced no substantial change in Zn content of the tissues. An increase occurred in eggs and hepatopancreas during the first six days of depuration. During exposure to Cd and Zn combined (40 micrograms Cd/L + 70 micrograms Zn/L), tissue Zn levels responded as with Zn alone. In the presence of Zn, Cd concentration was doubled in the hepatopancreas, depressed by one-third in the carcass, and did not change in the other tissues. Increased amounts of Zn (up to 410 micrograms Zn/L) had not effect on the Cd levels of the tissues except that the Cd level in the hepatopancreas was depressed, although the level was still greater than in the case of exposure to Cd alone. The possible role of metallothionein is discussed.