Effect of zinc deficiency on the accumulation of metallothionein and cadmium in the rat liver and kidney

The effects of zinc (Zn) deficiency and repeated exposure to cadmium (Cd) on the accumulation and distribution of metallothionein (MT), Cd and Zn in the liver and kidney were studied. Male Sprague-Dawley rats were fed either a Zn-deficient (1 ppm) or a Zn-adequate (40 ppm) diet during the experiment, and the rats were injected subcutaneously with a cadmium chloride solution (1.0 mg Cd/kg of body weight, 5 days a week) for 4 weeks. Cadmium, Zn, and Cd-induced MT concentrations in the liver and kidney were lower in the Zn-deficient rats (–Zn + Cd) than in the Zn-adequate rats (+ Zn + Cd), while the content of Cd bound to high molecular weight proteins (HMWP) was greater in the Zn-deficient rats (–Zn + Cd). The Zn bound to Cd-induced MT was reduced to 30% in the liver and to 60% in the kidney of the Zn-deficient rats (–Zn + Cd) as compared with that of the Zn-adequate rats (+ Zn + Cd). In the kidney of Zn-deficient rats, exposure to Cd caused a decrease in essential Zn associated with HMWP as compared with that of Zn-adequate rats (+ Zn + Cd). Thus, Zn-deficiency affected the distribution of Cd in tissues, MT and HMWP and accelerated substantially Cd-induced Zn-deficiency in the kidney. Although the renal Cd concentration was lower in the Zn-deficient rats (–Zn + Cd) than in the Zn-adequate rats (+ Zn + Cd), exposure to Cd for four weeks resulted in glucosuria and an increase in liver and kidney weights in the Zn-deficient rats (–Zn + Cd), but not in the Zn-adequate rats (+ Zn + Cd). These results suggest that development of Cd toxicity is related to the Zn status of the body, to the accumulation of Cd in HMWP and to the amount of essential Zn associated with HMWP.     

Effect of hyperoxia on oxygen free radical defense enzymes in the lung of zinc-deficient rats

The effects of hyperoxia and the response of oxygen free radical defense enzymes in the lung and extracellular environment of the lung were measured in Zn-deficient rats. Although lung was the target organ as indicated by the increased lung:body weight ratio in all hyperoxia-exposed rats regardless of dietary regimen, 85% oxygen exposure seemed to impose a stress on the whole animal as indicated by decreased feed intake and body weight in ad libitum-fed rats. Hyperoxia exposure superimposed on Zn deficiency did not further reduce the feed intake or body weight of Zn-deficient rats. After 7 d of hyperoxia exposure, the Zn-repleted and ad libitum-fed groups consistently had increased activity of lung CuZn-superoxide dismutase (CuZnSOD), glutathione peroxidase and catalase; but changes in CuZnSOD activity were not related to lung Cu or Zn concentrations. Although Zn-deficient and pair-fed rats were unable to increase CuZnSOD activity, they had an increased lung Zn concentration compared with their air-exposed counterparts. Hyperoxia exposure also caused an increase in ceruloplasmin activity of pair-fed and ad libitum-fed control rats. We concluded that dietary Zn repletion started at the beginning of 85% oxygen exposure was effective for increasing the activity of the lung oxygen free radical defense enzymes, thus preventing hyperoxia-induced lung damage in Zn-deficient rats.     

Effects of magnesium and zinc deficiencies on growth and protein synthesis in skeletal muscle and the heart.

The effects of magnesium or zinc deficiency on growth, tissue contents of Mg or Zn and protein synthesis have been compared in 4-13-week-old rats. When maintained on Mg-deficient fodder (1.6 mmol/kg) or Zn-deficient fodder (27 mumol/kg) rats showed a reduced weight gain, whereas repletion caused increased growth rates. Pair-feeding experiments showed that this could not be attributed to reduced energy intake only. In rats maintained on Mg-deficient fodder for 14 d [3H] leucine incorporation into skeletal muscle and the heart was reduced by 24-38% compared with pair-fed controls (P less than 0.001-0.002). The incorporation of [3H]phenylalanine was reduced by 19-31%. Tissue Mg contents, however, were only reduced by 6-7% (not significant). The pair-fed rats showed no reduction in the [3H]leucine incorporation compared with ad lib.-fed animals. In rats maintained on Zn-deficient fodder for 15 d [3H]leucine incorporation into skeletal and heart muscle was reduced by 57-64% compared with pair-fed controls. The pair-fed rats showed no reduction in the [3H]leucine incorporation compared with ad lib. fed animals. In the Zn-deficient animals the content of Zn was not reduced in the skeletal muscles, whereas there was a small (15%) but significant loss of Zn in the heart. In another experiment, Zn depletion for 17 d caused a reduction in [3H]leucine incorporation of 35-41%. After 5 d of Zn repletion this defect was restored, and the [3H]leucine incorporation was above control level in the skeletal muscles. It is concluded that the intact organism is very sensitive to dietary Mg or Zn deficiency, and that the reduced growth and protein synthesis cannot easily be attributed to the reduction of tissue Mg or Zn content per se. This points to the existence of other control mechanisms mediating down-regulation of growth and protein synthesis in response to reduced dietary supplies and the ensuing drop in the plasma concentrations of Mg and Zn.     

The effects of zinc deficiency on turnover of cadmium-metallothionein in rat liver

The object of this experiment was to determine the effects of Zn deficiency on the turnover of Cd-induced metallothionein (MT) in rat liver. Male rats were fed a purified Zn-deficient or Zn-adequate diet. After 13 days, the rats were given three daily injections of Cd2+ totaling 1.5 or 3.0 (Zn-deficient) and 3.0 or 6.0 (Zn-adequate) mg Cd/kg body weight. The MT was labeled by injecting the rats with [35S]cystine 2 hours after the final Cd injection. One, 3 or 5 days after labeling, the rats were killed, and their livers were assayed for MT 35S and metal content. The metal composition of MT (mole %) was 41-42% Cd, 51-54% Zn and 4-7% Cu in the Zn-adequate groups and 64% Cd, 27-31% Zn and 6-9% Cu in the Zn-deficient groups. The half-lives of Cd-induced MT in the Zn-deficient rats were 2.6 days (1.5 mg Cd/kg) and 2.8 days (3.0 mg Cd/kg). In the Zn-adequate rats, the half-lives were 3.6 days (3.0 mg Cd/kg) and 3.1 days (6.0 mg Cd/kg). The half-lives of general, soluble hepatic proteins were 4.1 to 4.3 days in all groups. Despite the stabilizing effect of the higher Cd content, the half-life of hepatic MT in the Zn-deficient rats was significantly shorter than in the Zn-adequate rats. These results indicate that hepatic MT degradation is faster in Zn-deficient animals.     

Intestinal microflora, morphology and enzyme activity in zinc-deficient and Zn-supplemented rats

1. Immature, male Wistar rats were given a low-zinc diet (2 mg/kg) for 22-24 d. Control groups received a similar diet supplemented with 58 mg Zn/kg either ad lib., or in amounts matched to the consumption of the Zn-deficient group. Food consumption, rate of growth and food conversion efficiency were markedly lower in the Zn-deficient group of rats compared with controls. Appetite, growth rate and food utilization improved dramatically over a subsequent 4 d period of Zn supplementation. 2. Morphological examination of samples of jejunum and ileum confirmed that Zn deficiency in the rat is accompanied by a reduction in villous dimensions and increase in villous density. After a short period of Zn supplementation, villous density and the basal width and maximum height of individual villi in the jejunum returned to normal. Similar changes occurred in the ileum but to a lesser extent. 3. Mucosal alkaline phosphatase (EC 3.1.3.1) activity was significantly lower in the small intestine of Zn-deficient rats compared with Zn-supplemented rats. Disaccharidase activities were lower in the Zn-deficient group, compared with their feed-restricted counterparts, but were similar to values for ad lib.-fed controls. Tissue alkaline phosphatase and disaccharidase activities were consistently higher after a 4 d period of Zn supplementation, compared with non-supplemented animals, but this increase was only significant for alkaline phosphatase. 4. Although there were striking similarities in the mucosal characteristics of gnotobiotic and Zn-deficient rats, there was no indication that even severe dietary Zn depletion reduced the numbers of viable bacteria present in either the small or large intestine.(ABSTRACT TRUNCATED AT 250 WORDS)     

Zinc-induced metallothionein and copper metabolism in intestinal mucosa, liver, and kidney of rats

Large doses of parenteral zinc (Zn) and/or the feeding of high Zn diets to animals or humans for long periods affects copper (Cu) metabolism. Previous work suggests that Zn-induced metallothionein (MT) in intestinal epithelial cells binds Cu and inhibits its absorption. This study was designed to determine the effects of treating rats with high dietary or parenteral Zn on Cu metabolism and its relationship to MT in the intestinal epithelium, liver and kidney. Six-week-old male rats were fed for one week a control diet containing 42 mg Zn and 6 mg Cu/kg. They were then divided into three groups. One group continued to receive the control diet while another received a similar diet containing 560 mg Zn/kg. A third group, fed the control diet, received a subcutaneous dose of 90 mg Zn/kg body weight every 2–3 days for the duration of the experiment. Rats from each group were killed on days 7 and 14. Low Cu status in Zn-treated rats was indicated by lower than normal serum Cu concentration, serum ceruloplasmin activity, low liver and kidney Cu concentrations and low cytochrome C oxidase activity. None of these changes, however, were related to an increase in Cu as a result of Zn-induced MT in the intestinal epithelial cell. Instead, as the MT concentrations rose, Cu concentration decreased. This study suggests that the effects of high Zn treatment on Cu status are not the result of the long-held theory that Zn-induced intestinal MT sequesters Cu and prevents its passage to the circulation. Instead, it may be caused by a direct effect of high lumenal Zn concentrations on Cu transport into the epithelial cell.     

Dietary repletion can replenish reduced T cell subset numbers and lymphoid organ weight in zinc-deficient and energy-restricted rats

The objective of the present study was to investigate the time course for recovery of lymphoid tissue and T cell subset numbers when Zn-deficient (ZD) or energy-restricted (ER) rats were repleted with control diet; in a second experiment, the link between the stress axis and lymphoid organs was explored. During the deficiency phase, rats were fed a ZD (<1 mg Zn/kg) or control diet (30 mg Zn/kg, nutritionally complete) either as pair-fed controls (ER) or ad libitum-fed controls (CTL) for 3 weeks. During the repletion phase, all rats were fed control diet ad libitum for 3, 7 or 23 d. After the deficiency phase, ZD and ER had lower T cell subset numbers in the thymus compared with CTL, and ZD had reduced T cell subset numbers in the spleen compared with both ER and CTL. T cell subset numbers and lymphoid organ weights recovered from dietary Zn deficiency and energy restriction by 7 d of repletion (except 23 d for thymus weight in ZD), while body weight required more than 23 d for recovery. At the end of the deficiency phase, ZD and ER had higher circulating corticosterone concentrations compared with CTL; plasma TNFalpha was not detectable and there were no differences in plasma haptoglobin, an acute-phase protein. In conclusion, Zn deficiency and energy restriction elevated circulating corticosterone and reduced T cell subset numbers in the thymus and spleen of growing rats. Repletion with a nutritionally complete diet allowed recovery of T cell subset numbers and lymphoid organ weight.     

Changes in dietary zinc result in specific alterations of metallothionein concentrations in newborn rat liver

To investigate the role of metallothionein (MT) in the sequestration and storage of zinc in newborn rat livers, a cross-fostering experiment was performed in which zinc-deficient (Zn-D) pups were suckled from Zn-sufficient (Zn-S) dams and vice versa. At consecutive days during lactation, groups of pups were killed. The experiment was continued for 22 d. Zinc concentrations in various tissues and MT concentrations in livers and kidneys were analyzed. The retention of injected 65Zn, as well as body weight, was also studied in both groups. Higher whole-body retention of 65Zn in the zinc-depleted (Zn-Dp) rats indicates a decreased zinc turnover. These rats also showed markedly reduced growth. The observation that the zinc-repleted (Zn-Rp) pups, although showing 65Zn retention similar to that of controls, grew less than controls suggests that Zn-Rp may not compensate for gestational zinc deficiency. Zn-Rp pups showed an increased accumulation of zinc into hepatic MT until d 10, whereas Zn-Dp pups showed a more accelerated degradation of MT than controls. These data indicate that hepatic MT levels fluctuate directly in response to dietary zinc status in newborn rats. Various tissues such as spleen, heart, lung and intestine showed no difference in zinc concentration among all groups at d 22 postpartum. Thus the rapid degradation of hepatic MT in zinc deficiency that may occur to maintain the required zinc levels in other tissues supports the role of MT as a zinc storage protein in newborn rats.     

Development of alimentary zinc deficiency in growing rats is retarded at low dietary protein levels

The aim of the present study was to determine whether the level of dietary protein would influence the onset of zinc deficiency in rats because zinc-deprived rats have problems metabolizing dietary protein. Young male Sprague-Dawley rats were fed isoenergetic Zn-deficient diets (0.8 mg Zn/kg diet) or control diets substituted with zinc sulfate (54 mg Zn/kg diet) and protein levels of 2, 5, 8, 10, 15, 20 or 25 g/100 g for 21 d to determine whether changing the protein level of Zn-deficient diets affects the Zn status of the rats. In rats fed low dietary protein levels of 2 and 5%, feed intake, growth and appearance did not differ between the Zn-deficient rats and the control rats because the low zinc requirement was met by mobilization of zinc from the skeleton. At higher dietary protein levels, the Zn-depleted rats developed marked signs of Zn deficiency and had reduced feed intake, growth, alkaline phosphatase activity in the serum and Zn concentrations in serum and femur compared with the control rats. The reduced feed intakes and decreased growth of Zn-depleted rats fed high dietary protein levels (20 and 25%) compared with control rats may be due to disturbed protein synthesis, as demonstrated by the increased activities of alanine aminotransferase, glutamate dehydrogenase and carbamoylphosphate synthetase in the liver. Zinc as an essential component of the diet is thus vital for the efficient utilization of dietary protein.     

Effect of zinc deficiency on the pregnant ewe and developing foetus

Mature Merino ewes were given either a low-zinc diet (4 mg/kg) or an adequate-Zn diet (50 mg/kg) for all or part of pregnancy. The ewes consuming the low-Zn diet consumed 25% less feed than those given the adequate-Zn diet during the last 115 d of pregnancy. Zn concentration in the plasma of Zn-deficient pregnant ewes declined from 0.7 to 0.3 mg/l. The lambs born to Zn-deficient ewes weighed less and had reduced concentrations of Zn or less total Zn, or both, in the whole carcass, liver and pancreas. A reduction in activity of alkaline phosphatase (EC 3.1.3.1) in the liver and a slight reduction in thymidine kinase (EC 2.7.1.21) activity in the thymus was also observed in Zn-deficient lambs. The Zn-deficient ewes deposited approximately 63 mg Zn into each single-born lamb; this indicates that during the last third of pregnancy the developing foetuses were accumulating the equivalent of 35% of the total dietary Zn intake of the ewes.     

Dietary oxidised fat up regulates the expression of organic cation transporters in liver and small intestine and alters carnitine concentrations in liver, muscle and plasma of rats

It has been shown that treatment of rats with clofibrate, a synthetic agonist of PPARalpha, increases mRNA concentration of organic cation transporters (OCTN)-1 and -2 and concentration of carnitine in the liver. Since oxidised fats have been demonstrated in rats to activate hepatic PPARalpha, we tested the hypothesis that they also up regulate OCTN. Eighteen rats were orally administered either sunflower-seed oil (control group) or an oxidised fat prepared by heating sunflower-seed oil, for 6 d. Rats administered the oxidised fat had higher mRNA concentrations of typical PPARalpha target genes such as acyl-CoA oxidase, cytochrome P450 4A1 and carnitine palmitoyltransferases-1A and -2 in liver and small intestine than control rats (P < 0.05). Furthermore, rats treated with oxidised fat had higher hepatic mRNA concentrations of OCTN1 (1.5-fold) and OCTN2 (3.1-fold), a higher carnitine concentration in the liver and lower carnitine concentrations in plasma, gastrocnemius and heart muscle than control rats (P < 0.05). Moreover, rats administered oxidised fat had a higher mRNA concentration of OCTN2 in small intestine (2.4-fold; P < 0.05) than control rats. In conclusion, the present study shows that an oxidised fat causes an up regulation of OCTN in the liver and small intestine. An increased hepatic carnitine concentration in rats treated with the oxidised fat is probably at least in part due to an increased uptake of carnitine into the liver which in turn leads to reduced plasma and muscle carnitine concentrations. The present study supports the hypothesis that nutrients acting as PPARalpha agonists influence whole-body carnitine homeostasis.     

Growth and zinc homeostasis in the severely Zn-deficient rat

Male weanling rats were fed on diets either adequate (55 mg/kg), or severely deficient (0.4 mg/kg) in zinc, either ad lib. or in restricted amounts in four experiments. Measurements were made of growth rates and Zn contents of muscle and several individual tissues. Zn-deficient rats exhibited the expected symptoms of deficiency including growth retardation, cyclic changes in food intake and body-weight. Zn deficiency specifically reduced whole body and muscle growth rates as indicated by the fact that (a) growth rates were lower in ad lib.-fed Zn-deficient rats compared with rats pair-fed on the control diet in two experiments, (b) Zn supplementation increased body-weights of Zn-deficient rats given a restricted amount of diet at a level at which they maintained weight if unsupplemented, (c) Zn supplementation maintained body-weights of Zn-deficient rats fed a restricted amount of diet at a level at which they lost weight if unsupplemented (d) since the ratio, muscle mass: body-weight was lower in the Zn-deficient rats than in the pair-fed control groups, the reduction in muscle mass was greater than the reduction in body-weight. Zn concentrations were maintained in muscle, spleen and thymus, reduced in comparison to some but not all control groups in liver, kidney, testis and intestine, and markedly reduced in plasma and bone. In plasma, Zn concentrations varied inversely with the rate of change of body-weight during the cyclic changes in body-weight. Calculation of the total Zn in the tissues examined showed a marked increase in muscle Zn with a similar loss from bone, indicating that Zn can be redistributed from bone to allow the growth of other tissues. The magnitude of the increase in muscle Zn in the severely Zn-deficient rat, together with the magnitude of the total losses of muscle tissue during the catabolic phases of the cycling, indicate that in the Zn-deficient rat Zn may be highly conserved in catabolic states.     

Altered ex vivo cytokine production in zinc-deficient, pair-fed and marginally zinc-deficient growing rats is independent of serum corticosterone concentrations

The objective of the present study was to examine the effects of dietary Zn deficiency on the ex vivo cytokine production (IL-2, interferon-gamma (IFN-gamma), IL-6 and IL-10) of isolated thymocytes and splenocytes after mitogenic stimulation with concavalin A and to explore the role of corticosterone in this regulation. Weanling rats were assigned to one of four dietary treatments for 3 weeks: Zn-deficient (< 1mg Zn/kg diet, ad libitum), pair-fed (30 mg Zn/kg diet, limited to amount of feed as consumed by the Zn-deficient group), marginally Zn-deficient (10 mg Zn/kg diet, ad libitum) and control (30 mg Zn/kg diet, ad libitum). Thymocytes and splenocytes were isolated for cytokine stimulation and determination of T-cell phenotypes. Serum corticosterone concentrations were determined by ELISA. The Zn-deficient and pair-fed groups had 14-fold higher serum corticosterone concentrations compared with the marginally Zn-deficient and control groups (P<0.0001). The proportions of thymocyte subsets were not altered in the Zn-deficient, pair-fed or marginally Zn-deficient groups; however, thymocyte IL-2 and IL-6 production in these groups was 33-54% lower compared with the control group (P<0.05). The Zn-deficient group had an 18-28% lower proportion of new T-cells (TCRalphabeta+CD90+), but no difference in the proportion of new T-cells that were cytotoxic or helper. The Zn-deficient group had a 49-62% lower production of Th1 cytokines (IL-2), but no difference in the production of Th2 cytokines (IL-6, IL-10) by stimulated splenocytes compared with the pair-fed, marginally Zn-deficient and control groups (P<0.01). These results indicate that Zn status is associated with altered cytokine production, while in vivo corticosterone concentrations are not associated with ex vivo cytokine production.     

Intestinal cellular proliferation and protein synthesis in zinc-deficient rats

Immature male Wistar rats were given a low-zinc semi-synthetic diet (2 mg Zn/kg) for 28 d. Control groups received a similar diet supplemented with 58 mg Zn/kg either ad lib. or in amounts matched to the consumption of the Zn-deficient group. Rates of growth, food consumption and small intestinal length were significantly reduced in the Zn-depleted rats. Zn deficiency in the rat was associated with a reduction in the ratio, crypt: villus and a lower rate of crypt cell division in the jejunum. This resulted in a substantial decrease in the net influx of new cells into the villi of the Zn-deficient animals compared with controls. The fractional rates of protein synthesis in jejunal mucosa were measured by a technique based on the determination of L-[4-3H]phenylalanine incorporation. There was no evidence of a decline in the protein synthetic rate in total mucosa from Zn-deficient rats. It is suggested that a reduction in cell influx into the villi may be responsible for the morphological and functional changes observed in the small intestine of rats fed on a low-Zn diet.     

Effect of dietary zinc or copper deficiency on the primary free radical defense system in rats

The effect of dietary Zn or Cu deficiency on the primary free radical defense system was examined in the lungs and livers of 6-wk-old rats. Enzymatic components (superoxide dismutase, catalase and glutathione peroxidase) and nonenzymatic components (alpha-tocopherol, ascorbate, glutathione and metallothionein) of the primary free radical defense system, as well as tissue concentrations of Cu, Zn and Fe, were measured. Liver CuZn-superoxide dismutase and liver catalase activities were significantly lower (P less than 0.05), and lung metallothionein and liver ascorbate concentrations were significantly higher (P less than 0.05) in Cu-deficient rats than in either pair-fed or ad libitum-fed controls. Zn-deficient rats had a significantly lower (P less than 0.05) concentration of liver metallothionein than either control group. Other changes in the enzymatic and nonenzymatic components of the primary free radical defense system could be attributed to the reduction in feed intake by Zn- or Cu-deficient rats and not to a direct effect of the Zn or Cu deficiency per se. The primary free radical defense system in lung and liver of severely Zn- or Cu-deficient rats was not seriously compromised.     

The effect of dietary zinc depletion and repletion on rats: Zn concentration in various tissues and activity of pancreatic gamma-glutamyl hydrolase (EC 3.4.22.12) as indices of Zn status

Unlike severe zinc deficiency, marginal Zn deficiency is difficult to identify in rats because no reliable indicator of suboptimal Zn status is currently available. We have previously observed reduced pancreatic gamma-glutamyl hydrolase (EC 3.4.22.12) activity and impaired pteroylpolyglutamate absorption in Zn-deficient rats. In the present study the effect of Zn depletion and repletion on the Zn concentration of various tissues and on the activity of this enzyme was investigated. The objective was to determine the sensitivity of these variables to Zn depletion and to evaluate their usefulness as indices of Zn status. Male Wistar rats (about 180 g), maintained from weanling on a purified Zn-adequate diet, were randomly allocated into twelve groups. A pretreatment control group was killed immediately. The remaining eleven groups were fed on a Zn-deficient diet and a group killed daily for 7 d (Zn-depleted groups). The remaining four groups were re-fed the Zn-adequate diet and a group killed daily (Zn-repleted groups). On analysis, pancreas and spleen Zn levels responded most rapidly to reduced Zn intake, followed by tibia, liver, kidney and plasma. Zn concentration was maintained in testes. Reduced plasma folate levels were also observed. A significant reduction in pancreatic gamma-glutamyl hydrolase activity before the depletion of many tissue Zn stores confirms the Zn sensitivity of the enzyme. It was concluded that future investigation into the inter-relationship between Zn and folate metabolism may be useful in identifying a sensitive, biochemical index of Zn status.     

Effect of various intakes of phylloquinone on signs of vitamin K deficiency and serum and liver phylloquinone concentrations in the rat

The relationship between dietary phylloquinone, serum and liver concentrations of phylloquinone, and various indices of vitamin K adequacy have been studied in male rats fed a purified diet containing various levels of phylloquinone. In excess of 500 micrograms phylloquinone/kg diet was needed to prevent the most sensitive signs of vitamin K deficiency. Liver phylloquinone concentrations were shown to be correlated with dietary phylloquinone intake. Serum phylloquinone was not correlated with either diet or liver concentration of phylloquinone and did not increase with increased dietary intake until the liver contained sufficient vitamin to maintain optimal synthesis of vitamin K-dependent proteins. Because of the rapid loss of vitamin from the liver, prior ingestion of a high level of vitamin K had little influence on liver vitamin K concentrations beyond the first 2 d of a deficient period. When rats consumed a diet containing 500 micrograms phylloquinone/kg diet in 3 h, liver and serum phylloquinone concentrations fluctuated drastically following this feeding period. During the subsequent 24-h period, liver phylloquinone concentrations decreased to a level that would not support maximal activity of the hepatic vitamin K-dependent carboxylase.     

Maternal iron and zinc supplementation during pregnancy affects body weight and iron status in rat pups at weaning

Pregnant women worldwide are frequently iron (Fe) and zinc (Zn) deficient. Therefore, cosupplementation with Fe and Zn during pregnancy is common. Although Fe supplementation programs are successful, studies suggest that Zn supplementation negatively affects maternal Fe metabolism. However, little is known about the effects of maternal Fe or Zn supplementation on Fe metabolism in the offspring. We developed a rat model to investigate if Fe and/or Zn supplementation during pregnancy affects regulation of nonheme Fe absorption and Fe status in offspring and if these effects are dependent upon maternal Fe and Zn status at conception. Control (C; fed a Fe- and Zn-adequate diet; 75 and 25 μg/g, respectively) or Fe- and Zn-deficient (D; fed a Fe- and Zn-deficient diet; 12 and 10 μg/g, respectively) rats were supplemented with Fe (27 mg/wk), Zn (4.5 mg/wk), Fe+Zn (27 mg Fe, 4.5 mg Zn/wk), or placebo throughout pregnancy. At postnatal d 21, body weight (BW), hemoglobin (Hb), hematocrit (Hct), liver and intestine Fe concentration, liver hepcidin, and intestine Fe transporter expression were determined in pups. Zn supplementation of C dams decreased pup BW (P < 0.0001), whereas it increased pup BW in D dams (P < 0.0001). Zn supplementation of C dams did not affect Hb and Hct in pups but increased the liver Fe concentration (P = 0.0002). However, Zn supplementation of D dams decreased hepcidin expression in their offspring (P < 0.0001). In C dams, Fe and Fe+Zn supplementation decreased ferroportin levels in pup intestine compared with pups from unsupplemented dams (P < 0.05). In conclusion, Zn supplementation of dams with adequate Fe and Zn status increases offspring liver Fe concentration and postnatally compromises BW. Therefore, potential adverse effects of Zn supplementation should be evaluated.     

Effect of cadmium on hepatic metallothionein level in early development of the rat

The induction of hepatic metallothionein (MT) was investigated 24 hr after an intraperitoneal injection of 0.75 mg/kg Cd as CdCl₂ · H₂O in rats of 7, 14, 21, and 90 days. Metallothionein in liver cytosolic fractions collected on Sephadex G-75 was characterized in terms of sulfhydryl, total protein, Cd, and Zn contents. Most of the cytosolic Cd was associated with MT and the concentration of Cd was equal in the different age groups. The higher contents of sulfhydryl, protein, and Zn both in control as well as in Cd-injected rats of 7 and 14 days than in those of 21 and 90 days indicate the presence of more native Zn-thionein in immature pups. However, the increase in sulfhydryl and protein contents showed more prominent induction of MT in Cd-exposed animals of 21 and 90 days than in those of 7 and 14 days. The concentration of Cd was highest in liver followed by the other tissues. While hepatic accumulation of Cd was similar in all age groups, the renal accumulation increased significantly with age. The intestine and spleen of immature pups concentrated more Cd than those of mature animals. The accumulation of the metal did not differ significantly in heart and brain of the animals among the four groups.