Dietary Zinc Levels Research Articles

Feeding diets supplemented with zinc and vitamin A in laying hens: effects on histopathological findings and tissue mineral contents

The effects of different dietary levels of zinc and vitamin A on tissue mineral accumulation and histopathological alterations were examined in laying hens. For this purpose, 130 Hisex brown laying hens aged 56 weeks were divided into two main groups. Each group of hens were fed on diets supplemented with two different levels of vitamin A (0–10 000 IU kg −1). Then, laying hens in both of the main groups were subdivided into five treatment groups given different levels of zinc (0, 25, 50, 100, and 200 mg kg −1) for 12 weeks. Dietary additions of zinc and/or vitamin A did not significantly affect the zinc concentrations of the pancreas, liver, gizzard, thyroid, and copper concentrations of the pancreas, gizzard, and thyroid. The group fed the highest zinc (200 mg kg −1) in the diet had twofold iron concentration in their thyroid tissue compared to the concentration of the control group receiving no extra zinc. Histopathologically, there was slight oedema, degranulation, and vacuolation in exocrine cells and some fibrotic areas in the pancreas and reduced follicular size. Follicular cell hypertrophy and hyperplasia occurred in the thyroids, and gizzard erosions were seen in some cases.

Dietary carbohydrate, iron and zinc interactions in Atlantic salmon ( Salmo salar)

Atlantic salmon (initial weight 312 g) were fed four experimental diets containing either low (5%) or high (10%) levels of wheat starch, combined with either a low (6 mg kg −1) or high (30 mg kg −1) iron and zinc level, in order to elucidate interactions between dietary starch and iron plus zinc. No difference in specific growth rate or protein productive value as a consequence of the variations in dietary starch was observed. Protein efficiency ratio was significantly lower in fish fed with 5% compared to 10% starch diets, indicating higher deposition of nonprotein components as a consequence of the higher starch level. Dietary iron plus zinc significantly influenced final weight, condition factor and hepatosomatic index, with lower values in fish fed with higher mineral levels. The present dietary manipulations did not affect blood haematology, with all values being within normal ranges for Atlantic salmon. Plasma levels of glucose, protein, cholesterol or triacylglycerols were not affected by the dietary treatments. Low activities of plasma aspartate amino transferase and alanine amino transferase indicated, along with no mortality, no negative effects on liver function or fish health due to dietary treatments. Glycogen levels in whole body, liver and spleen were increased in fish fed with 10% compared to 5% starch diets. Liver iron concentration was affected by both dietary starch and mineral levels. Whole body homogenates showed significantly higher zinc levels in fish fed with higher iron and zinc diets, whereas plasma zinc levels were affected by dietary starch, iron and zinc levels, which showed a significant interaction effect.

The effect of dietary iron levels on changes in iron status and zinc-dependent enzyme activities in rats fed two levels of dietary zinc.

In order to determine the interrelationship between dietary iron and zinc levels, the effects of dietary iron levels (2, 10, 20, and 40 microg/g) on changes in iron and zinc status and zinc enzyme activities (aminolevulinic acid dehydratase ALA-D EC 4.2.1.24 and alkaline phosphatase ALK-P EC 3.1.3.1) in male Wistar rats were investigated using adequate and marginally deficient zinc diets (25 and 5 microg/g). When rats were fed 5 microg Zn/g diets, body weight gain and food intake remained unchanged at a Fe diet intake of 20 microg/g or greater. Similar tendencies were obtained for hemoglobin, hematocrit, plasma iron, and transferrin saturation. In contrast, liver, spleen, and femur iron concentrations increased gradually with increased iron intake. Feeding diets containing 25 microg Zn/g did not alter these parameters. The percentages of apparent iron absorption in both dietary zinc groups tended to increase with decreasing dietary iron and attained maximum levels at an Fe intake of 10 microg/g. However, In the case of rats fed Fe at concentrations of 2 microg/g Iron absorption decreased. Regardless of the dietary zinc level, rats fed diets with an Fe concentration of 2 microg/g had decreased zinc absorption and plasma ALK-P activity. However, ALA-D activity was not influenced by dietary iron.

Evaluation of daily dietary intake and serum level of zinc and copper in children of high risk families for premature cardiovascular disease

Evaluation of daily dietary intake and serum level of zinc and copper in children of high risk families for premature cardiovascular disease

Induction of metallothionein by exposure to normobaric 100% oxygen atmosphere in rats with different zinc supply

The objective of this study was to determine the effects of an oxygen enriched environment on the induction of the metalloprotein metallothionein (MT) and its relation to zinc metabolism in rats supplied with different levels of dietary zinc. Male albino rats were fed purified diets based on maize starch, egg white, saccharose and soybean oil differing in the concentration of zinc (1; 20; 100; 500 mg Zn/kg diet). At a dietary zinc supply of 1 mg/kg, the rats developed a zinc deficiency indicated by visual and biochemical parameters. At the end of the 37-day feeding period, half of the rats were exposed to 100% oxygen for 12 h.The oxygen treatment significantly reduced plasma zinc in the zinc supplemented rats and reduced it in tendency in the zinc deficient rats. The MT concentration was increased in the zinc supplemented groups in the liver, kidney and lung. The oxygen treatment elevated the metallothionein concentration in the two high zinc supplemented groups (100 and 500 mg Zn/kg diet) in the liver. The response of the zinc concentration in plasma and of hepatic metallothionein levels to oxygen exposure indicates a role of metallothionein in zinc distribution or interactions with other trace elements to support antioxidant capacity, rather than an impact on direct scavenging activity of free radicals.

Zinc methionine and zinc sulfate as sources of dietary zinc for juvenile abalone, Haliotis discus hannai Ino

A feeding experiment was conducted to determine the minimum dietary zinc requirement of juvenile abalone, Haliotis discus hannai, with zinc methionine (ZnMet) and zinc sulfate (ZnSO 4·7H 2O) as the zinc sources and to compare the bioavailability of the two zinc sources using a premium quality diet based on casein–gelatin as the protein sources. Semipurified experimental diets containing graded levels of dietary zinc (5.6–84.6 mg zinc/kg) provided as either ZnMet or ZnSO 4 were fed to juvenile abalone in triplicate groups for 16 weeks. The results showed that the average weight gain rate (WGR, %), daily increment in shell length (DISL, μm/day), soft-body alkaline phosphatase activity (SBAKP, U/g protein) and soft-body zinc concentration (SB zinc, μg/g) of the abalone were significantly (ANOVA, P<0.01) affected by dietary treatment, and responded in broken-line models to increases in dietary zinc levels from the two zinc sources. The requirements for dietary zinc using ZnMet and ZnSO 4 as the supplemental zinc sources, determined by broken-line regression analysis, on the basis of maximum WGR were 15.49 and 34.10 mg/kg, respectively, on maximum DISL were 15.16 and 33.99 mg/kg, respectively, on maximum SBAKP were 15.54 and 31.91 mg/kg, and on maximum SB zinc deposition were 17.75 and 34.29 mg/kg, respectively. The shell zinc concentration, as well as iron concentration in soft-body and shell of the abalone, however, was maintained relatively constant (ANOVA, P>0.05) regardless of dietary treatment. Based on these results, a minimum requirement for dietary zinc was recommended to be 16–18 mg/kg from ZnMet, and 35 mg/kg from ZnSO 4. This experiment also showed that the bioavailability of dietary zinc with ZnMet was approximately three times as high as that of ZnSO 4 to H. discus hannai Ino.

THE INFLUENCE OF ELEVATED DIETARY ZINC, SELENIUM, AND THEIR COMBINATION ON THE SUPPRESSIVE EFFECT OF DIETARY AND INTRAPERITONEAL CADMIUM ON EGG PRODUCTION IN LAYING HENS

The influence of elevated dietary zinc and/or selenium on the suppressive effect of cadmium on egg production in hens has not been previously established. To address this question, two models of cadmium administration were used to differentiate protective effects of zinc or selenium that may result from a reduced absorption of cadmium from those resulting from an elevated nutritional status of these minerals. First, cadmium-induced suppression of egg production was produced in White Leghorn hens using intraperitoneal injections of Cd in order to determine protective effects that result from prefeeding diets supplemented with 803 ppm Zn, 0.91 ppm Se, or their combination relative to a basal diet (control). Feeding elevated dietary selenium throughout the experiment, including a 6-day prefeeding period before Cd administration, resulted in significant protection from the egg suppression produced by 2 injections of cadmium (0.27 mg/ kg each) given 1 d apart. Feeding elevated dietary zinc alone or combined with +0.91 ppm Se for a similar period did not markedly protect against cadmium-induced egg suppression. After a 0.54- mg/ kg dose of Cd was administered, for a cumulative dose of 1.08 mg/ kg, no significant protection was observed from any of the supplemented diets. In a second experiment, the protective effect of the same dietary treatments on the egg-suppressive effect of dietary cadmium was determined. In contrast to cadmium injection, the suppressive effect of 153 ppm dietary cadmium was not mitigated by selenium supplementation, while supplemental zinc protected against this effect of dietary cadmium regardless of the amount of selenium in the diet. There was no significant change in plasma estrogen and vitellogenin levels as a result of cadmium administration in either model, with the exception of significant reduction in both these parameters in the dietary cadmium-exposed birds fed the basal diet. Together, the data suggest that the level of dietary zinc in food sources may be more important in influencing cadmium-induced egg suppression than the nutritional status of zinc in cadmium-exposed birds. In contrast, the nutritional status of selenium in cadmiumexposed birds may have the potential to mitigate this effect, but high exposures to dietary cadmium or zinc may preclude such protection.

Integrative Aspects of Zinc Transporters

Cells maintain zinc concentrations with relatively narrow limits. Nevertheless, physiologically relevant changes in free Zn(II) pools or changes in Zn bound to specific ligands or within vesicles may occur without a major change in total cellular zinc concentrations. The task of maintaining such levels rests in part with zinc transporter proteins. The genes for some putative zinc transporters have recently been cloned. As of this time, most have not been directly shown to transport zinc in functional studies, albeit evidence is strong that they have such a function. Zinc transporter (ZnT)-1 was identified as a rescue agent for cells maintained in very high extracellular zinc conditions; therefore, ZnT-1 has been suggested to function as an exporter. ZnT-1 is expressed in a variety of tissues, including intestine, kidney and liver. Intestinal expression is regional, being much greater in duodenum and jejunum and in villus versus crypt cells. Immunolocalization places ZnT-1 at the basolateral membrane of intestinal enterocytes and epithelial cells of the distal renal tubules. Regulation of ZnT-1 mRNA and ZnT-1 protein does not change markedly with changes in dietary zinc level except when a large single oral zinc supplement is provided. ZnT-1 is induced by transient ischemia of the forebrain. ZnT-2 and ZnT-3 may function in tissue-specific vesicular zinc transport. ZnT-4 is believed to be abundant in mammary gland and may be associated with zinc secretion into milk. A mutation of the ZnT-4 gene may account for the lethal milk (lm) syndrome. The putative zinc transporters identified thus far appear to have characteristics commensurate with functions in integrative zinc acquisition and homeostasis.

Reduction in carbonic anhydrase activity in the tongue epithelium and submandibular gland in zinc-deficient rats.

We investigated the effects of zinc deficiency on carbonic anhydrase (CA) activity in the tongue epithelium and submandibular gland in rats. Male 4-week-old SD rats were given free access to a diet containing 2.2 (zinc-deficient), 4.1 (low-zinc), or 33.7 (zinc-sufficient) mg zinc/kg diet for 6 weeks. Rats in the fourth group (receiving 33.7 mg zinc/kg) were pair-fed against the zinc-deficient rats. Biochemical analysis at the end of the experimental period indicated that zinc deficiency significantly reduced CA activity in the tongue epithelium and submandibular gland, and the CA activity levels in these tissues seemed to parallel the dietary zinc levels. By enzyme histochemistry, an intensely positive reaction for CA was observed in the middle and basal regions of the taste buds in the circumvallate papilla in the zinc-sufficient and pair-fed (control) rats. The cells in von Ebner's glands also showed a strong positive reaction in control rats, although only a weak reaction product was found in zinc-deficient rats. These results suggest that CA activity is affected by the dietary content of zinc, which is considered to be an indispensable factor for the maintenance of normal taste sensation.

Plasma Apolipoprotein B-48, Hepatic Apolipoprotein B mRNA Editing and Apolipoprotein B mRNA Editing Catalytic Subunit-1 mRNA Levels Are Altered in Zinc-Deficient Rats

Apolipoprotein B (apoB) exists as two major isoforms and serves as an obligatory component of lipid-rich plasma lipoprotein particles. Apolipoprotein B mRNA editing is a zinc-dependent, site-specific cytidine deamination that determines whether the apoB-100 or apoB-48 isoform is synthesized. The objective of this work was to examine whether dietary zinc levels affect apoB mRNA editing in vivo. Adult male Sprague-Dawley rats were randomly assigned to zinc-deficient (ZD, <0.5 mg Zn/kg diet), zinc-adequate (ZA, 30 mg Zn/kg diet) or zinc-replenished (ZDA, ZD rats fed the ZA diet for last 2 d) dietary groups for 18 d. The ratio of plasma apolipoprotein B-48 (apoB-48) to total apoB was significantly lower in zinc-deficient compared with zinc-adequate rats. Primer extension analysis indicated a modest but significant reduction in hepatic apoB mRNA editing in ZD rats compared with that of the ZA group. In ZDA rats, hepatic apoB mRNA editing and the percentage of plasma apoB-48 to total apoB were not different from ZA rats. The mRNA abundance of hepatic apobec-1 (apoB mRNA editing catalytic subunit 1) was significantly lower in ZD and ZDA rats than in ZA rats. In summary, the plasma ratio of apoB-48 to total apoB protein as well as hepatic apoB mRNA editing and hepatic apobec-1 mRNA levels were reduced in rats consuming a zinc-deficient diet. These data suggest that one or more components of apoB metabolism may be influenced by dietary zinc status.

Influence of Supplemental Manganese and Zinc on Live Performance and Carcass Quality of Broilers

An experiment was conducted to evaluate the influence of varying levels of dietary manganese (Mn) and zinc (Zn) on broiler production. Corn-soybean meal type feeds were supplemented with either 0:0, 60:50, 120:100, or 180:150 ppm inorganic Mn:Zn and fed throughout 49 days of production. At 49 days of age, all birds wee subjected to pre-slaughter handling typical of industry practice, processed on automated equipment, and manually deboned on stationary cones. Measurements assessed live performance, carcass quality, and skeletal integrity. Supplemental levels of Mn:Zn did not influence either broiler performance or carcass quality. Skeletal integrity was similarly unaffected.

Dietary protein quality and zinc levels in growing rats

Previous studies from our laboratory have shown that the intake of a low quality dietary protein during either a short or a long period, causes thymus atrophy of growing rats with a significant reduction in the number of cells and the mature T cell population. Moreover, thymus atrophy was associated with Zinc deficiency. The aim of this study was to determine if the intake of this diet induced a concomitant Zinc deficiency. Rats of the Wistar strain were fed from weaning and during 10 days a 6.5% maize protein diet (M10) or a 6.5% casein diet (C10). An age-matched control group was run simultaneously (C). The only dietary variable was the protein quality, being the Zinc content the same. Food intake (g/day) was similar: (M10: 6.5±1.4, C10: 6.8±1.1). Zn levels were determined by atomic absorption spectrophotometry in plasma (P), whole blood (WB), liver (L) and thymus (T) and expressed as μg/ml and μg/g wet tissue, respectively. No differences were found in WB (M10: 3.85±0.24, C10: 3.88±1.00, C: 3.67±0.34) nor L (M10: 42.50±11.30, C10: 36.30±6.70, C: 39.10±8.60). However, P levels decreased in M10 and C10 when compared to C (M10: 1.84±0.63, C10: 1.79±0.41, C: 2.43±0.37, P<0.04) while a significant increase in thymus Zn was only found in M10 compared to C10 and C (M10: 40.00±13.20, C10: 26.50±2.70, C: 27.10±3.60, p<0.01). These results show that the intake of a low quality dietary protein might alter the distribution of plasma Zinc with a concomitant uptake of Zinc by the thymus.

Biomonitoring of contaminated mine tailings through age accumulation of trace metals in the bank vole (Clethrionomys glareolus).

Lead, zinc and cadmium were determined in a range of tissues from laboratory-bred bank voles (Clethrionomys glareolus) exposed to elevated levels of dietary zinc (124 micrograms g-1). The pelletised diet was derived from vegetation harvested from the surface of a revegetated tailings dam at a modern Zn-Pb mine. Exposure regimes to the contaminated diet were 16, 32, 64, 128 or 256 days. Elevated levels of dietary zinc were not reflected in the individual tissue or total body concentrations. Marginal age accumulation of lead and cadmium was evident in the liver (Pb) and kidney (Pb and Cd). Tissue residues did not attain toxicologically significant concentrations. Animals inhabiting the grassland are considered to be at low ecotoxicological risk with respect to trace metals.

Current Zinc Intake and Risk of Diabetes and Coronary Artery Disease and Factors Associated with Insulin Resistance in Rural and Urban Populations of North India

Objective: To determine the association between current zinc intake and prevalence of coronary artery disease (CAD) and diabetes as well as factors associated with insulin resistance.Design, Subjects and Methods: In this cross sectional survey, 3575 subjects, aged 25 to 64 years, including 1769 rural (894 men, 875 women) and 1806 urban (904 men, 902 women) subjects were studied. The survey methods included questionnaires for 7-day food intake record, physical examination, and electrocardiography using World Health Organization criteria.Results: The prevalence of CAD, diabetes and glucose intolerance was significantly higher among subjects consuming lower intakes of dietary zinc. There was a higher prevalence of hypertension, hypertriglyceridemia and low high-density lipoprotein cholesterol levels which showed significant upward trend with lower zinc intakes. Serum lipoprotein (a) and 2-hour plasma insulin levels also were associated with low zinc intake. Multivariate logistic regression analysis after adjustment for age showed that zinc intake and CAD were inversely associated. Serum zinc (odds ratio:men 0.77, women 0.57), serum triglycerides (men 0.86, women 0.81), blood pressure (0.83 men, women 0.76), diabetes mellitus (men 0.90, women 0.85), central obesity (men 0.88, women 0.87), glucose intolerance (men 0.66, women 0.57) and low high-density lipoprotein cholesterol (men 0.72, women 0.70) were significant risk factors for CAD (explained by tertiles of zinc status) in urban subjects. These associations were not observed in rural subjects.Conclusion: Lower consumption of dietary zinc and low serum zinc levels were associated with an increased prevalence of CAD and diabetes and several of their associated risk factors including hypertension, hypertriglyceridemia and other factors suggestive of mild insulin resistance in urban subjects.

Performance and tissue zinc and metallothionein accumulation in chicks fed a high dietary level of zinc

Four experiments were conducted to identify several factors that might improve the accuracy and reproducibility of Zn bioavailability assays for chicks. Response of tissue Zn and metallothionein (MT) concentrations to various elevated levels and soluble sources of dietary Zn were measured, as well as the effect of delaying high Zn administration until 7 d posthatching to alleviate the detrimental effect of Zn sulfate on feed intake to 3 wk of age. Bone Zn increased (P < 0.01) in all experiments in response to increasing dietary Zn concentrations. Liver and pancreas MT were affected (P < 0.01) by a source by age interaction and variability that made this criterion unsuitable for bioavailability assays. Lastly, 1-d-old chicks were used to study the effect of delaying feeding of a high-Zn diet up to 7 d of age. The basal diet was fed continuously for 21 d as a control. A diet containing 1,000 ppm Zn was either fed continuously from Day 1, or started on Day 3, 5, or 7. Chicks given high Zn on Day 3, 5, or 7 decreased (P < 0.01) feed intake within 24 h of feeding. Delayed feeding of high dietary Zn might help to alleviate decreased feed intake observed in previous studies. Delaying the onset of high Zn feeding by several days may help alleviate feed intake problems observed with Zn sulfate. Use of either Zn gluconate or Zn acetate as a standard in assays or use of MT synthesis as a bioavailability criterion will probably not be useful to improve accuracy of the estimates.

Influence of dietary zinc on convulsive seizures and hippocampal NADPH diaphorase-positive neurons in seizure susceptible EL mouse

Adequate, high and deficient dietary levels of zinc (Zn) were compared in seizure-susceptible EL mice with respect to convulsions and to nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase-positive hippocampal neurons. Diaphorase positivity is associated with nitric oxide (NO) production. Convulsive seizures in the EL mice given the various diets did not differ over 1–4 weeks, but convulsions in EL mice given the Zn-deficient diet for 4 weeks were more effectively suppressed by injection of zonisamide (ZNS) (75 mg/kg intraperitoneally) than in mice receiving high- or adequate-Zn diet for the same period. Numbers of NADPH diaphorase-positive neurons in the CA1/CA2 region of the hippocampal formation were significantly higher in mice given the Zn-deficient diet for 4 weeks than in mice fed adequate Zn. Mice receiving the high-Zn diet for the same period had significantly fewer NADPH diaphorase-positive neurons in the subiculum than mice with adequate Zn. These results suggest that Zn deficiency inhibits convulsive seizures of EL mice, and that dietary Zn influences numbers of NO producing neurons in the hippocampal formation.

Plasma and Erythrocyte Zinc Concentrations and their Relationship to Dietary Zinc Intake and Zinc Supplementation During Pregnancy in Low-Income African-American Women

Objective To evaluate the effects of usual dietary intake of zinc and of zinc supplementation during pregnancy on plasma and erythrocyte zinc concentrations. Design A randomized, double-blind, placebo-controlled trial. Subjects Low-income African-American women (n=580) assigned randomly to groups at 19 weeks of gestation. Intervention A daily dose of zinc (25 mg) or a placebo until delivery. Main outcome measures Plasma, erythrocyte, and dietary zinc levels. Statistical analyses Multiple regression and repeated measures analysis of variance. Results In both the placebo and the supplemented groups, when all subjects were grouped by usual dietary zinc intake above or below the median (12 mg/day), results were the same: Women with high dietary zinc intake had higher erythrocyte zinc levels at the time of randomization and at all subsequent measurements during pregnancy than those who had low dietary zinc intake ( P≤.06; difference not significant for zinc-supplemented group); no difference was observed for plasma zinc levels. On the other hand, when the subjects were stratified at the median by total daily zinc intake (usual dietary zinc + 25 mg zinc supplement) during pregnancy, a significant difference in plasma zinc levels ( P<.005) was found between women with high total zinc intake (mean=38 mg/day) and low total intake (mean=13 mg/day) at 26, 32, and 38 weeks of gestation; however, no such differences were found in erythrocyte zinc levels. Applications These results should help dietitians and other health professionals better understand the expected changes in plasma and erythrocyte zinc levels during pregnancy, and the relationship between dietary and supplemental zinc and zinc nutriture. J Am Diet Assoc. 1997;97:1296-1274.

Immune Response and Resistance of Channel Catfish toEdwardsiella ictaluriChallenge when Fed Various Dietary Levels of Zinc Methionine and Zinc Sulfate

Abstract The effects of dietary levels of zinc from zinc methionine (ZnM) and zinc sulfate ZnSO4 on nonspecific immune responses and disease resistance of juvenile channel catfish Ictalurus punctatus (mean initial weight of 3.3 g) were determined. Fish in triplicate aquaria were fed to satiation twice daily for 16 weeks with an egg white basal diet without zinc supplementation or supplemented with 5, 20, and 60 mg zinc/kg as ZnM or 20 and 60 mg zinc/kg as ZnSO4. Relative percentages of peripheral blood lymphocytes, thrombocytes, and macrophages were not affected by dietary zinc. The relative percentages of neutrophils significantly increased in fish fed 20 and 60 mg Zn/kg as ZnM. Chemotactic responses of macrophages were significantly higher for fish fed the three ZnM-supplemented diets and the 60-mg ZnSO4. Dietary zinc, however, had no influence on the phagocytic activity of macrophages for Edwardsiella ictaluri. Likewise, neither the source nor the level of dietary zinc provided protection to channel ca...

Differential expression of cysteine-rich intestinal protein in liver and intestine in CCl4-induced inflammation.

Cysteine-rich intestinal protein (CRIP) is a double zinc finger (LIM domain) protein that is developmentally regulated but has an unknown function. CRIP is highly expressed in the intestine, but expression is low in liver. To determine if CRIP expression is regulated under altered physiological status, we used CCl4-induced injury as a model to produce hepatic injury and systemic effects associated with inflammation. Since CRIP is a zinc finger protein and zinc decreases the hepatic response to CCl4, the effect of supplemental dietary zinc (300 mg/kg diet) was also examined. Our results show that this supplemental level of dietary zinc did not affect the index of hepatic injury (plasma alanine aminotransferase), indicating zinc did not have a protective effect. Liver CRIP mRNA increased with CCl4 and CRIP protein was shown by immunohistochemistry to be localized in hepatocytes near the vascular supply. In the intestine, CCl4 caused a transient decrease in CRIP mRNA, but supplemental dietary zinc treatment prevented this decrease. These current results show that CRIP expression changes in response to cellular damage due to acute hepatic injury and are consistent with a functional role for CRIP in proliferation, differentiation, or turnover.

Effects of different levels of dietary zinc on the gilthead, Sparus aurata during the growing season.

Gilthead were fed three diets. Diet A was the control diet, whereas diets B and C were supplemented with 300 and 900 mg Zn/kg, respectively. Fish fed with diet C, at the end of the experiment, showed the lowest weight. Zinc concentrations presented the higher values in gills, liver, and kidney. Muscle and brain had the lower mean values and showed a tight control of zinc levels. These results reinforce the hypothesis that zinc in the CNS should be strictly controlled in order to maintain the functional role of the metal. Significant differences in tissue zinc concentrations were obtained between fish fed different amounts of zinc, the metal concentrations being higher in tissues of fish fed diet C. The tissue decrease of zinc, found at the end of the experiment, may depend on a lower feed consumption or on different zinc requirements during the cold season. These changes, even if not univocal among the three diets, may be associated with the life cycle of fish. Furthermore, copper concentrations were little affected by the different concentrations of zinc in the three diets; liver and kidney presented the highest concentrations; liver showed a significant decrease in copper content at the end of the experiment. We conclude that: zinc concentrations of the diet may affect the gilthead weights and the tissual metal content; and zinc concentrations in the diets, depending on the growth rate, may be varied depending on the season.