Tissue Zn Concentrations Research Articles

Iodine and/or selenium deficiency alters tissue distribution pattern of other trace elements in rats.

Tissue distribution of Fe, Mn, Cu, and Zn, the essential trace elements associated with oxidant and/or antioxidant processes, was examined in iodine- and/or selenium-deficient rats (ID, SeD, ISeD). Fe and Mn were the most affected minerals in all types of deficiency states. Mn levels decreased significantly in the liver in all deficiency states (approx 20-30%), in the heart in ID and SeD rats (approx 30-35%) and in the testis in ID rats (approx 15%). Whereas Mn enhancement was noted in kidney (approx 45%) and plasma in SeD and ISeD (approx 20% and 50%, respectively) animals. However, most striking alterations were seen with Fe. Significant elevation of Fe concentrations were observed in all deficiency states in the kidney (approx 90-125%) and heart (approx 20-25%), and in the liver in SeD (approx 35%) and ISeD (approx 75%) rats, whereas significant (approx 20%) Fe enhancement in the testis was observed only in ISeD animals. Lower Cu (approx 10-15%) and higher Zn (approx 10-20%) concentrations in heart tissues in all deficiency states were found; higher Zn (approx 20-35%) in the kidney of SeD and ISeD rats, and lower Cu in the testis of SeD animals were observed. In brain tissue, no alteration was seen in Fe, Mn, and Zn content, however, significantly increased (approx 15-20%) Cu concentrations were noted in all deficiency states. The results of this study indicated that iodine and/or selenium deficiency may modify the distribution and the homeostasis of other minerals.

Zinc and copper status in acute pancreatitis: an experimental study.

Metal ions are required as active components of several proteins, including pancreatic enzymes, and they can play important roles in the etiopathogenesis of acute pancreatitis. In the present study, we measured the concentrations of zinc (Zn) and copper (Cu) in both serum and pancreatic tissue, as markers of trace element status in an experimental acute pancreatitis model. Twenty-four male Wistar rats were divided into two groups: the experimental group (N=24) and the control group (N=10). Acute pancreatitis was induced by injection of 48% ethyl alcohol into the common biliary duct. The animals were sacrificed 24 h later to detect the concentrations of Zn and Cu. There was no significant difference in tissue Zn and Cu concentrations between control and experimental groups (p<0.05). However, in the acute pancreatitis group, serum Zn and Culevels were very significantly lower (p<0.001 and p<0.0001, respectively). In conclusuion, these findings suggested that altered mineral metabolism in serum and pancreatic tissue may have contributed to the pathophysiology of acute pancreatitis.

Effect of long-term swimming exercise on zinc, magnesium, and copper distribution in aged rats.

Trace element content of different tissues might be altered by both age and exercise training. We aimed to determine the effects of a 1-yr swimming protocol (60 min/d, 5 day/wk) on tissue levels and the distribution of zinc (Zn), magnesium (Mg), and copper (Cu) in aging rats. Three groups were formed: sedentary and trained old groups and a young control group. Tissue Zn, Mg, and Cu concentrations were measured in the kidney, heart, liver, lungs, and gastrocnemius and soleus muscles. Kidney zinc concentration significantly decreased in the sedentary old group compared to the young control group (p<0.01) and was significantly higher in the trained old group compared to the sedentary old group (p<0.01), whereas Zn levels in the soleus muscle significantly increased in the sedentary old group in comparison to young controls (p<0.05). Tissue Mg concentrations remained unchanged. The sedentary old group exhibited a significant decrease in kidney Cu concentration compared to the young control group (p<0.01). Although kidney Cu levels also decreased in trained old rats in comparison to young controls (p<0.05), they were significantly higher than in sedentary old rats (p<0.01). The decrease in kidney Zn and Cu content as a result of aging was partly prevented by long-term swimming exercise.

Development of iron deficiency decreases zinc requirement of rats.

Effects of the development of Fe deficiency on changes in Fe and Zn metabolism and its possible interactions with dietary Zn were determined. Adequate (25 microg/g) and marginally deficient (5 microg/g) Zn diets containing a sufficient (40 microg/g) dietary Fe levels were fed for 2 wk. Thereafter, both dietary Zn groups were fed an Fe-deficient (2.2 microg/g) diet for 4 wk. It was found that the effects of an Fe-deficient diet began to occur 7 and 14 d after feeding the Fe-deficient diet. At this time, tissue Fe concentrations were depleted and rats were unable to maintain hemoglobin levels. The Fe-deficient diet also induced an immediate fall in plasma Fe concentration, transferrin saturation, and apparent Fe absorption, while the concentrations of liver cytochrome c increased as Fe deficiency developed. Decreases in liver and spleen Fe levels, as well as the activities of blood and bone marrow aminolevulinic acid dehydratase (ALA-D, EC 4.2.1.24) were observed 3, 7, and 14 d after feeding the Fe-deficient diet, and thereafter they were increased. On the other hand, the activity of plasma alkaline phosphatase (ALK-P, EC 3.1.3.1) decreased continuously as Fe deficiency progressed. With severe development of Fe deficiency, rats fed the Zn-adequate diet had increased levels of Zn concentration in the plasma, liver, spleen, kidney, and femur, whereas apparent Zn absorption was decreased. The decrease in apparent Zn absorption and the increase in tissue Zn concentration of rats might be related to the lowered Zn requirement, which is associated with the depressed Zn metabolism caused by feeding Fe-deficient diets.

Appraising zinc bioaccumulation in abalone Haliotis diversicolor supertexta and alga Gracilaria tenuistipitata var. liui by probabilistic analysis

We appraise a first-order two-compartment model describing zinc (Zn) bioaccumulation in abalone Haliotis diversicolor supertexta and their food source, red alga Gracilaria tenuistipitata var. liui by probabilistic analysis of the biokinetic parameter variabilities. The model was parameterized using field and laboratory data, and predictions were quantitatively compared with field-measured tissue Zn concentrations obtained from selected abalone farms. Based on the reliable information from the published literature, we assigned the lognormal distribution model to characterize model inputs. Input variables included bioconcentration factor (BCF) of abalone, biomagnification factor of abalone, BCF of algae and depuration rate constants of abalone ( k 2) for Zn from water and food. Compared with the field data, most of the measurements fall within the predicted 25th and 75th percentile range, indicating applying Monte Carlo technique to the first-order two-compartment model generated probabilistic estimates of Zn concentrations in abalone and algae that were consistent with field observations. Sensitivity analysis reveals that the input critical parameters that most influence the model output are BCF and k 2 of abalone. Our results suggest that the probabilistic approach allows a range of possible outcomes and their likelihood; it better informs both aquacultural risk assessors and risk managers. The degree of conservatism in the deterministic bioaccumulation models can also be evaluated against this distribution.

Effect and possible role of Zn treatment in LEC rats, an animal model of Wilson's disease

The effect of oral zinc (Zn) treatment was studied in the liver, kidneys and intestine of Long–Evans Cinnamon (LEC) rats in relation to metals interaction and concentration of metallothionein (MT) and glutathione (GSH). We also investigated the change in the activity of antioxidant enzymes and determined the biochemical profile in the blood and metal levels in urine. We showed that the Zn-treated group had higher levels of MT in the hepatic and intestinal cells compared to both untreated and basal groups. Tissue Zn concentrations were significantly higher in the Zn-treated group compared to those untreated and basal, whereas Cu and Fe concentrations decreased. The antioxidant enzyme activities in the Zn-treated group did not change significantly with respect to those in the basal group, except for hepatic glutathione peroxidase activity. Moreover, the biochemical data in the blood of Zn-treated group clearly ascertain no liver damage. These observations suggest an important role for Zn in relation not only to its ability to compete with other metals at the level of absorption in the gastrointestinal tract producing a decrease in the hepatic and renal Cu and Fe deposits, but also to MT induction as free radical scavenger.

Phytostabilization of Metal Mine Tailings Using Tall Fescue

Mined areas near the city of Galena, Kansas, provide a source of heavy metal contamination, particularly cadmium (Cd), lead (Pb), and zinc (Zn). The metals move off-site in response to erosion by wind and running water, spreading the contamination beyond its original extent. Phytostabilization of the mine tailings could limit the spread of these heavy metals. The purpose of this study was to attempt field-scale inoculation of tall fescue (Festuca arundinacea Schreb) with mycorrhizal fungi to enhance growth and survival on a metal-contaminated mine spoil, and to study the influence of cattle manure as a soil amendment on basic soil chemical properties and on the chemical fractionation of Cd, Pb, and Zn. No evidence of successful infection by mycorrhizal fungi was found. After the first growing season, vegetative cover reached 71% but then steadily declined to 29% over the next two growing seasons. Extractable soil phosphorus (P) levels remained constant throughout the study and were sufficient for normal plant growth. Extractable potassium (K) levels declined throughout the study and were not sufficient for normal plant growth after the third year. Soil pH decreased from an average of 7.9 early in the study to 6.5 at the end. Plant tissue Zn concentrations suggested Zn phytotoxicity that became worse over the course of the study. Manure increased the amount of organically bound metals and generally decreased exchangeable levels. Between the first and third years of the study, exchangeable forms of metals generally increased while residual forms decreased. These changes are likely the result of the soil acidification that occurred during this same period, and may have contributed to the decline in fescue productivity because of increased problems with Zn phytotoxicity.

Evaluating Helix aspersa as a sentinel for mapping metal pollution

The common garden snail has been proposed as a sentinel species for mapping environmental concentrations of toxic metals, since it accumulates high levels in its soft tissues. The capacity of Helix aspersa to quantify site differences is assessed here from a survey of 23 populations around UK and Wales with a wide range of contamination. Five adult snails were collected from each site during 1 week in 1990. Each replicate snail was partitioned into two soft tissue components (the hepatopancreas and the ‘rest’) and their Pb, Cd, Cu and Zn levels compared with those in the soil (as an integrative long-term measure of exposure) and the leaves of one food plant, Taraxacum (as a measure of recent dietary exposure). Median concentrations in one or both tissue fractions correlated with both soil and vegetation levels for each metal except Cu. Whole soft tissue Zn, Pb and Cd concentrations were also correlated with either soil or Taraxacum or both. However, Cd and Zn levels were not independent of tissue dry weight and there were also interference effects between Pb, Cd and Zn in the ‘rest’ and between Cd and Zn in all fractions. Lead in the hepatopancreas correlated with both soil and dietary sources, and was independent of dry weight. There was some correlation of Cd with Pb in this tissue. Outliers largely determined the relationship between hepatopancreatic Pb and both soil Pb and vegetation Pb. If sites with very high levels in each source were excluded from the analysis, the significant correlation of hepatopancreatic Pb with vegetation and soil concentrations disappear. This study emphasizes that sentinels have to do more than simply rank sites by their tissue concentrations: a prime criterion in their selection should be their capacity to quantify the magnitude of site differences.

In Situ Stabilization of Soil Lead Using Phosphorus and Manganese Oxide

In situ stabilization of Pb contaminated soils can be accomplished by adding P and Mn(IV) oxide. However, the long-term efficacy of in situ stabilization under continual P removal through plant growth is unknown. Moreover, the effects these treatments have on phytoavailability of other metals (Cd and Zn) commonly associated with Pb in soil are not well understood. Greenhouse experiments using sudax [Sorghum vulgare (L.) Moench] and Swiss chard [Beta vulgaris (L.) Koch] were carried out to evaluate the effects of plant growth on soil Pb bioavailability to humans after addition of P and other amendments, and the effects of these treatments on Pb, Cd, and Zn phytoavailability in three metal-contaminated soils. Eight treatments were used: zero P; 2500 mg of P as triple superphosphate (TSP); 5000 mg of P as TSP or phosphate rock (PR); 5000 mg of Mn oxide/kg; and combinations of Mn oxide and P as TSP or PR. The addition of P and/or Mn oxide significantly reduced bioavailable Pb, as measured by the physiologically based extraction test (PBET), in soils compared with the control even after extensive cropping. The PBET data also suggested that removal of P from soluble P sources by plants could negate the beneficial effects of P on bioavailable Pb, unless sufficient soluble P was added or soluble P was combined with Mn oxide. In general, Ph, Cd, and Zn concentrations in shoot tissues of sudax and Swiss chard were reduced significantly by TSP and did not change with the addition of PR. The combination of PR and Mn oxide significantly reduced Pb concentrations in plants compared with the control.

Interactions between Zn and Cu in LEC rats, an animal model of Wilson's disease.

The effect of oral Zn treatment was studied in the liver and kidneys of 26 male Long-Evans Cinnamon (LEC) rats (mutant animals, 5 weeks old) in relation to both the interaction between Zn and Cu and the localisation and concentration of metallothionein (MT). Rats receiving 80 mg zinc acetate daily by gavage and control rats receiving no treatment were killed after 1 or 2 weeks. By immunohistochemical and analytical chemical techniques we revealed that treated rats had higher levels of MT in the hepatic and renal cells compared to untreated ones. Tissue Zn concentrations were significantly higher in treated rats compared to untreated whereas Cu concentrations decreased in the liver and kidneys as indicated by analytical chemical analyses. MT levels also decreased with treatment period. A histochemical procedure, obtained using autofluorescence of Cu-metallothioneins, confirms these findings: after 2 weeks, the signal decreased in both the liver and kidney sections. This gives a greater understanding of the mechanism of Cu metabolism in the two tissues considered. These results suggest that Zn acts both to compete for absorption on the luminal side of the intestinal epithelium and to induce the synthesis of MT.

The effect of fertilizer additions on the solubility and plant-availability of Cd, Ni and Zn in soil

We conducted a pot experiment to investigate the effect of fertilizer additions on the solubility of Cd, Ni and Zn in soil solution and their uptake by plants. Radish (Raphanus sativus cv. Crystal Ball), oat (Avena sativa cv. Thule) and water spinach (Ipomoea aquatica cv. Kangkon) were grown in a naturally metal-rich soil. From day 7 after planting, fertilizers were added daily to each pot. Additions of fertilizer nutrients affected the pH of soil and soil solution, soluble and tissue concentrations of Ca, Mg, K, Cd, Ni and Zn differently in three plant species. The trend of soil and solution pH was in the order: water spinach < radish < oats, that resulted highest soluble and plant tissue concentrations of Cd and Zn in the water spinach followed by radish and then oats. However, Ni concentration in the soil solution increased in all pots and was not affected by pH changes. Soil solution pH increased by more than 1unit in the pots with radish and oats, indicating that mechanisms other than acidification, such as ion exchange and root exudation, may be responsible for the increased heavy metal uptake in these two plant species. Paired t-test showed significantly higher uptake of Cd and Zn in the radish plants resulting in lower concentrations of these elements in the solution. The contribution of mass flow to the supply of major cations and heavy metals varied among elements and plant species. Cadmium, Zn and K were taken up rapidly by all plant species in response to the amount supplied by mass flow. In contrast, the supply of Ni was in excess of its uptake by radish and water spinach. The uptake of all elements was positively correlated (p<0.0001) with mass flow and the transpiration rate in individual plant species. The study suggests that fertilizer cations increased the uptake of metals by improving growth conditions, but the magnitude of increase depended on plant species.

Effects of dietary chromium picolinate supplementation on serum and tissue mineral contents of laying Japanese quails

AbstractThis experiment was conducted to evaluate the effects of chromium (chromium picolinate, CrPic) on serum and tissue concentrations of Cr, Zn, Cu, Fe, and Mg of laying Japanese quails (Coturnix coturnix japonica). One hundred fifty laying Japanese quails (45 days old) were divided into five groups, 30 quails per group. The laying quails were fed either the control diet containing 1,285.96 μg of Cr/kg of diet or the control diet supplemented with 200, 400, 800, or 1,200 μg of Cr/kg of diet. Increasing dietary chromium supplementation linearly increased serum chromium and zinc concentrations (P = 0.01) but linearly decreased (P = 0.01) copper serum concentrations. Serum iron and magnesium concentrations did not change (P &gt; 0.10) as dietary chromium supplementation increased. Similar response to Cr supplementation was also observed in tissue mineral concentrations. Liver, longissimus muscle, and kidney chromium and zinc concentrations linearly increased (P = 0.01), whereas copper concentrations linearly decreased (P = 0.01) as dietary chromium supplementation increased. Also, liver, longissimus muscle, and kidney iron and magnesium concentrations did not change (P &gt; 0.10) as dietary chromium supplementation increased. The results of present study conclude that supplemental chromium to the diet of Japanese quails influences serum and tissue Cr, Zn, and Cu concentrations, thus most probably functions of the organs as well as the welfare of Japanese quails. J. Trace Elem. Exp. Med. 15:163–169, 2002. © 2002 Wiley‐Liss, Inc.

In Situ Stabilization of Soil Lead Using Phosphorus and Manganese Oxide

In situ stabilization of Pb contaminated soils can be accomplished by adding P and Mn(IV) oxide. However, the long-term efficacy of in situ stabilization under continual P removal through plant growth is unknown. Moreover, the effects these treatments have on phytoavailability of other metals (Cd and Zn) commonly associated with Pb in soil are not well understood. Greenhouse experiments using sudax [Sorghum vulgare (L.) Moench] and Swiss chard [Beta vulgaris (L.) Koch] were carried out to evaluate the effects of plant growth on soil Pb bioavailability to humans after addition of P and other amendments, and the effects of these treatments on Pb, Cd, and Zn phytoavailability in three metal-contaminated soils. Eight treatments were used: zero P; 2500 mg of P as triple superphosphate (TSP); 5000 mg of P as TSP or phosphate rock (PR); 5000 mg of Mn oxide/kg; and combinations of Mn oxide and P as TSP or PR. The addition of P and/or Mn oxide significantly reduced bioavailable Pb, as measured by the physiologically based extraction test (PBET), in soils compared with the control even after extensive cropping. The PBET data also suggested that removal of P from soluble P sources by plants could negate the beneficial effects of P on bioavailable Pb, unless sufficient soluble P was added or soluble P was combined with Mn oxide. In general, Pb, Cd, and Zn concentrations in shoot tissues of sudax and Swiss chard were reduced significantly by TSP and did not change with the addition of PR. The combination of PR and Mn oxide significantly reduced Pb concentrations in plants compared with the control.

Corrigendum to: Phosphorus efficiencies and their effects on Zn, Cu, and Mn nutrition of different barley (Hordeum vulgare) cultivars grown in sand culture

A sand-culture experiment was carried out in a growth chamber to investigate the phosphorus (P) efficiencies of 8 barley cultivars that are parents of 4 mapping populations, and the effects of P nutrition on plant uptake of zinc (Zn), copper (Cu), and manganese (Mn). Two sources of phosphate were used, rock phosphate (sparingly soluble) and CaHPO4 (readily available). There were significant differences in P uptake and utilisation efficiencies between the 8 cultivars. Among the cultivars, the Sahara–Clipper pair is of the most interest, because these 2 cultivars had large differences in root/shoot ratios, P allocation between root and shoot, and P uptake/utilisation efficiencies. Higher P availability significantly reduced plant Zn uptake and tissue concentrations in all cultivars. Shoot Zn concentrations were found to decrease significantly with P influx to the xylem (P &lt; 0.01), indicating that genotypic variations in P translocation from roots to shoots may interact with Zn accumulation in shoots. Higher P availability reduced Cu concentrations in shoots, probably due to a dilution effect. P availability (rock phosphate v. CaHPO4) seemed to affect plant uptake of Mn in some cultivars, but further study is needed to elucidate the mechanisms involved and the practical implications of this interaction in Mn-deficient soils.

Influence of variable zinc on yield, oil content, and physiology of sunflower

ABSTRACT Sunflower (Helianthus annuus L.) cv. Jwala Mukhi was grown until maturity in refined sand at variable levels of zinc ranging from acute deficiency to excess (0.00065 to 65 mg L−1). Both low (<0.065 mg L−1) and high (>0.065 mg L−1) zinc depressed the growth of sunflower. Foliar symptoms of zinc deficiency appeared on mature middle and old leaves of plants at 0.00065 and 0.0065 mg Zn L−1 as interveinal chlorosis and fading of green color from margins and apices. Later, leaf apices of the affected leaves turned necrotic and dry. Biomass, capitulum size, seed number, seed weight, concentration of chlorophylls a and b, and soluble proteins were maximum at 0.065 mg Zn L−1 (adequate), and were lowered significantly in both deficiency and excess of zinc. The effect of excess zinc (65 mg Zn L−1) on these parameters was more pronounced. An increase in zinc from low (0.00065 mg L−1) to high (65 mg Zn L−1) increased the activity of carbonic anhydrase (up to 6.5 mg Zn L−1) and decreased that of acid phosphatase in sunflower leaves. Zinc deficiency lowered the concentration of zinc and increased that of phosphorus in leaves. In sunflower seeds, the oil content was highest (23.4%) at 0.65 mg Zn L−1 and was reduced more by Zn excess than deficiency. In leaves, tissue Zn concentrations associated with deficiency, threshold of deficiency, threshold of toxicity and toxicity were 20, 30, 190, and 240 μg g−1 on a dry matter basis, respectively.

Relating the reproductive toxicity of five ingested metals in calanoid copepods with sulfur affinity

The sublethal toxicity of dietary Ag, Cd, Hg, Mn, and Zn to marine copepods, measured as depressed egg production, was evaluated as a function of ambient metal concentrations and metal concentrations in copepod tissues. All metals were toxic following 4-h feedings on metal-contaminated phytoplankton food, but there was a four order of magnitude difference between the inhibitory concentration in copepod tissues of the most toxic (2.4 nmol g −1 dry wt. for Hg) and least toxic (13.4 μmol g −1 dry wt. for Mn) metals. Metal concentrations in copepods that elicited a toxic response were about 3 times higher than background concentrations for Ag and 9 times higher for Hg, about 2 times higher for Cd, two orders of magnitude higher for Mn, and only 5% higher for Zn. Copepods exposed to lower concentrations of Zn for longer periods (1 week), resulting in tissue Zn concentrations similar to those in the short-term exposures, were not affected, suggesting that copepods were capable of adjusting to slowly increasing Zn by sequestration of this metal. Toxic metal concentrations in copepod tissues were directly proportional ( r 2=0.85) to the affinity of the metals for sulfur, as indicated by the solubility products of the metal sulfides. This relationship, together with protein analysis of eggs, published recently, suggests that metals affect egg production by binding to enzymes involved with vitellogenesis.

Zinc (Zn)-phosphorus (P) Interactions in Two Cultivars of Spring Wheat (Triticum aestivum L.) Differing in P Uptake Efficiency

Zinc-phosphorus (Zn-P) interactions were investigated in two wheat cultivars (Brookton and Krichauff) differing in P uptake efficiency. The experiment was carried out in a growth chamber. Rock phosphate or CaHPO4were used as P sources, and ammonium nitrate or nitrate only as nitrogen sources. Two Zn levels were used: 0.22 and 2.2mg ZnSO4.5H2Okg−1. The results confirmed that Brookton had a higher P uptake efficiency than Krichauff under low P conditions, irrespective of nitrogen and Zn supply. Zn supply had little effect on tissue P concentration and P uptake per unit of root weight in either cultivar, irrespective of nitrogen supply. An increase in P availability caused a significant reduction in Zn uptake per unit of root weight, and tissue concentration of Zn in both cultivars. The reduction in tissue Zn concentration cannot be explained entirely by a dilution effect. Zn uptake by, and Zn concentrations in, Brookton (with high P uptake efficiency) were significantly lower than those of Krichauff. Zn concentrations in Brookton were more sensitive to P uptake than those in Krichauff. It is suggested that high P uptake efficiency may depress plant uptake of Zn, and therefore cause a reduction in the concentration (density) of Zn in grains of wheats grown in low P (and possibly low Zn) soils.

ACCUMULATION OF METALS IN AUTOPSY TISSUES OF SUBJECTS LIVING IN TARRAGONA COUNTY, SPAIN

The concentrations of arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), lead (Pb), manganese (Mn), mercury (Hg), nickel (Ni), tin (Sn), vanadium (V) and zinc (Zn) were determined in autopsy tissues collected from subjects who at the time of death had lived in Tarragona (Catalonia, Spain) over a period of, at least, the previous 10 years. Samples of liver, lung, kidney, brain and bone were obtained from a total of 78 non-occupationally exposed subjects, autopsied between 1997 and 1999. Arsenic, Cd, Co, Cr, Cu, Pb, Mn, Hg, Ni, Sn, V and Zn were determined by inductively coupled plasma spectrometry (ICP/MS). The results were analyzed with respect to age, sex, smoking and drinking habits, and the subject's place of residence. Most tissue concentrations of As, Co, Cr, Hg and V were near to the analytical detection limit or, in some cases, even below it. However, the levels of Cu were slightly higher than the average concentrations found in other studies. Also, tissue concentrations of Mn, Sn and Zn were similar to those found in previous surveys, while those of Ni were lower than previously reported. Although the current levels of tissue Cd and Pb were comparatively lower than in studies in other areas, the distribution of both metals was similar to previously-reported trends. From the tissue metal concentrations observed in the present study, it would appear that neither environmental exposure nor a dietary excess of these elements could be considered a health hazard to people living in the study area.

Dietary Zinc Deficiency and Repletion Modulate Metallothionein Immunolocalization and Concentration in Small Intestine and Liver of Rats

Metallothionein (MT) functions in zinc (Zn) homeostasis and dietary Zn affects tissue MT concentration. The objective of this study was to investigate the effects of dietary Zn deficiency and 24-h Zn repletion on MT immunolocalization and concentration in the small intestine and liver of growing rats. Three-week-old rats fed Zn-deficient diet (< 1 mg Zn/kg) for 16 d had no MT staining in either small intestine or liver. After 24-h Zn repletion with control diet (30 mg Zn/kg), strong MT staining was observed in intestinal Paneth cells and surface epithelial cells in the proliferative regions of villi. Pair-fed control rats had strong MT staining in liver that was localized around central veins. After 24-h energy repletion, the hepatic MT staining diminished. Furthermore, Zn-deficient rats had significantly reduced intestinal (57%) and hepatic (61%) MT concentrations but unaffected Zn concentrations compared with controls that consumed food ad libitum. Zn repletion for 24 h restored intestinal and hepatic MT concentrations and reduced hepatic Zn concentration. Pair-fed control rats had elevated MT concentration in liver that was normalized by energy repletion. There was a significant positive correlation between tissue Zn and MT concentrations in liver (r = 0.60, P = 0.0001), but not in small intestine. In summary, MT immunolocalization and concentration in rat small intestine and liver were responsive to changes in Zn status, supporting the role of MT in Zn metabolism. Cell-type-specific localization of MT in small intestine after dietary Zn manipulations indicates a function of Zn and MT in gut immunity and intestinal mucosal turnover, and the pattern of hepatic MT distribution with energy restriction may be linked to detoxification processes.

Zinc Requirements of Annual Bluegrass and Creeping Bentgrass

Annual bluegrass (Poa annua L.) is becoming an important component of golf course putting greens. A greenhouse sand culture experiment was conducted to study the zinc (Zn) requirements of three genotypes of flowering annual bluegrass (FAB) and three genotypes of vegetative annual bluegrass (VAB), which were compared with the three parents of `Penncross' creeping bentgrass [Agrostis stolonifera L. (CB)]. Clonally propagated plants were grown in sand culture without Zn for 6 weeks prior to the initiation of the Zn treatments. The plants were then irrigated for 3 weeks with half-strength Hoagland's nutrient solution containing 0, 2.5, 5.0, or 40 mg·L-1 Zn from ZnSO4. Color was the only parameter affected by genotype; each genotype showed a significant quadratic response to increasing levels of Zn, with highest color ratings occurring at 2.5 mg·L-1. No genotypic differences were observed among CB, VAB, and FAB for shoot fresh and dry weight, root dry weight, or shoot tissue Zn concentrations. Shoot dry weight of all genotypes increased quadratically with Zn levels. Root dry weights of both VAB and FAB increased, while that of CB remained unchanged, as Zn level increased. Zinc concentrations in shoot tissue increased linearly as Zn level increased. Shoot Zn concentrations were higher in both VAB and FAB than in CB at each Zn level, but differences between VAB and FAB were insignificant. Maintaining shoot Zn concentrations below 109 mg·kg-1 in CB and 200 mg·kg-1 in VAB or FAB prevented Zn phytotoxicity from occurring.