Reevaluation of zinc deficiency on concanavalin-A-induced rat spleen lymphocyte proliferation

Zinc concentrations of serum, nonlymphoid and lymphoid tissues, and the responsiveness of concanavalin-A (Con-A)-stimulated spleen lymphocytes (SL) and cervical lymph node cells ( CLNC ) from ad libitum-fed zinc-deficient (ZD), pair-fed (PF) and ad libitum-fed zinc-adequate rats (AL) were determined. In vitro effects of serum from ZD, PF and AL rats on responsiveness of Con-A-stimulated SL and CLNC were determined. Weanling male Long-Evans rats were fed ad libitum zinc-deficient (less than 1.0 microgram Zn/g diet) and zinc-adequate (20 micrograms Zn/g diet) diets for 7-42 days. Effects of undernutrition on test parameters were determined on PF rats, which received a restricted zinc-adequate diet (restricted in amount to that consumed by ZD rats). Growth, food intake and zinc concentrations in serum, liver and pancreas were significantly depressed in ZD and PF rats. Zinc per gram of thymus tissue and per number of SL was elevated in ZD and PF rats. Spleen lymphocytes from ZD and PF rats displayed equivalent to significantly increased levels of proliferation following stimulation with Con-A. [3H]Thymidine incorporation by Con-A-stimulated SL and CLNC from ZD, PF and AL rats was not significantly different when cultured in medium containing serum from ZD, PF and AL rats. The present study shows that zinc deficiency causes major changes in total-body and organ growth but minor changes in zinc content and mitogen-induced proliferation of lymphocytes.     

Nitric oxide synthase inhibitor attenuates intestinal damage induced by zinc deficiency in rats

A nitric oxide synthase (NOS) inhibitor, NG-nitro-L -arginine methyl ester (L-NAME), was given to zinc-deficient (ZD) rats to determine whether it prevents the intestinal damage usually observed under these conditions. Weanling male rats were given free access to a ZD diet (2 mg zinc/kg), whereas control rats including pair-fed (PF) and ad libitum consumption (AL) groups were given a zinc-supplemented (50.8 mg zinc/kg) diet for 4 wk. Half of the ZD rats received L-NAME (0.3 g/L in drinking water) for 3 wk starting at the wk 2 of the deficient period. Plasma zinc concentration in ZD rats was significantly lower (P < 0.05) than that of AL and PF rats. Administration of L-NAME did not alter this concentration. Intestinal zinc concentration did not differ among groups. However, metallothionein-1 (MT-1) mRNA level was significantly lower in the intestine of ZD rats than in AL or PF rats. Treatment of ZD rats with L-NAME did not affect this level. Intestinal microvascular permeability evaluated by Evans blue showed significantly higher extravasation in ZD rats than in AL rats, whereas L-NAME administration inhibited the extravasation. Expression of inducible NOS mRNA was observed in intestine of ZD but not of AL or PF rats, and there was no significant difference between ZD rats, regardless of L-NAME treatment. The activity ratio of inducible NOS to total NOS in ZD rats not receiving L-NAME was significantly higher than that in AL rats or ZD rats treated with L-NAME (P < 0.05). The number of apoptotic-positive and goblet cells in intestinal villi was significantly higher in ZD rats compared with AL or PF rats. L-NAME administration in ZD rats reversed this effect. These results indicate that inhibition of NOS ameliorates zinc deficiency-induced intestinal damage in rats.     

The rate of rhodopsin regeneration in the bleached eyes of zinc-deficient rats in the dark

Rats fed a zinc-deficient, phytate-containing diet (ZD rats) for 4 wk showed typical signs of zinc deficiency: reduced food intake, slow weight gain, a poor food efficiency ratio and subnormal zinc concentrations in the serum, femur and eye. Pair-fed, weight-matched rats fed a zinc-sufficient diet (PF rats) showed normal serum zinc values, intermediate femur zinc levels and eye zinc concentrations similar to those in ZD rats. The vitamin A status of all three groups, expressed as the concentration of vitamin A in the liver, was comparable. After extensive bleaching, the initial rate of rhodopsin regeneration in ad libitum-fed, zinc-sufficient rats (AL rats), ZD rats and PF rats was the same, whereas the extent of rhodopsin regeneration in AL rats kept in the dark for 120 min was almost twice that found in ZD and PF rats. These results are not consistent with the hypothesis that zinc deficiency primarily affects dark adaptation by reducing the activity of alcohol dehydrogenase in the eye. Rather, zinc deficiency and the generalized malnutrition that results from markedly reduced food intake seem to depress the synthesis of opsin, and probably other proteins as well, in the rod cells of the eye.     

Reduced growth and skeletal changes in zinc-deficient growing rats are due to impaired growth plate activity and inanition

We investigated the effects of dietary zinc deficiency on skeletal metabolism in an animal model. Thirty 21-d-old male Sprague-Dawley rats were fed for 28 d either a zinc-deficient (ZD) diet (1 mg zinc/kg) or a normal diet ad libitum (AL, 50 mg zinc/kg) or in the same quantity as the ZD (pair-fed, PF). Only in the ZD group were general physical signs of zinc deficiency observed. Compared with the AL and PF rats, ZD rats showed significantly lower mean values in ponderal growth rate, femur weight and length, circulating levels of insulin-like growth factor-I, bone mechanical properties and concentration of zinc and, on histomorphometry, a decrease in the thicknesses of the overall growth plate and hypertrophic cartilage. In contrast, although bone volume was significantly lower in the ZD and PF rats than in the AL rats, no difference was observed between the ZD and PF rats. Osteoclast surface/bone surface and osteoclast number/bone surface ratios were significantly greater in PF rats than in the other two groups and not different in ZD and AL rats. Collectively, these data indicate that zinc deficiency has profound effects on the skeletal system of growing rats. In particular, the effects of zinc deficiency on bone growth and mass are the result of the reduced activity of the growth plate, likely mediated by impairment in the insulin-like growth factor-I system. We did not demonstrate an effect on bone mass via increased bone resorption.     

缺锌对0～2月龄大鼠免疫功能影响的研究

目的 观察缺锌对0～2月龄大鼠免疫器官及细胞因子分泌的影响,为进一步阐明缺锌影响免疫系统的机制及对婴幼儿期、青少年期合理补锌提供参考依据.方法 将9只Wistar孕鼠产仔后随机分为足锌(ZA)、对喂(PF)和缺锌(ZD)3组,每组3只母鼠.ZA组和PF组喂饲足锌饲料(30mg/kg),ZD组喂饲缺锌饲料(1.Omg/k...     

Influence of reduced food intake on polyunsaturated fatty acid metabolism in zinc-deficient rats

The influence of reduced food intake on metabolism of liver phospholipids (PL) in zinc-deficient (ZD) rats was measured. Wealing male Long-Evans rats were fed ad libitum zinc-deficient (2 micrograms Zn/g diet) and zinc-adequate (20 micrograms Zn/g diet) diets for 21 days. A pair-fed (PF) group was included. ZD and PF rats displayed significantly increased levels of linoleic (18:2 omega 6) and dihomo-gamma-linolenic acid (20:3 omega 6). Both ZD and PF rats displayed increased levels of gamma-linolenic acid (18:3 omega 6), but the increase was significant only in PF rats. ZD and PF rats displayed decreased levels of arachidonic acid (20:4 omega 6), but the decrease was significant only in PF rats. Both ZD and PF rats displayed significantly reduced levels of 22:5 omega 6. Both ZD and PF rats displayed increased products of delta 6 desaturation and decreased products of delta 5 and delta 4 desaturation. Significantly increased products of delta 9 desaturation were noted in both ZD and PF rats. ZD and PF rats displayed significant increases in C20 elongation products. ZD and PF rats displayed significantly decreased levels of omega 6 metabolites but not total omega 6 acids. ZD rats showed significantly increased levels of total omega 3 acids and omega 3 metabolites. ZD and PF rats showed significant increases in omega 9 acids but not significant changes in omega 9 metabolites. This study does not indicate that zinc affects the delta 6 desaturase in the metabolism of essential fatty acids. The aberrations previously attributed to zinc deficiency are probably due to the accompanying decreased food intake.     

锌对生长期大鼠海马Uch-L1表达的调控作用

目的探讨锌对生长期大鼠海马Uch-L1表达水平的调控作用。方法雄性断乳Wistar大鼠36只,按体重随机分为对照组(ZA)、缺锌组(ZD)和缺锌对喂组(PF),ZD组喂饲含锌量1.5mg/kg的缺锌饲料,PF组和ZA组喂饲含锌量30mg/kg的足锌饲料,PF组摄食量与ZD组一致。喂饲4周后,测定血浆锌含量和碱性磷酸酶活性以评价机体锌状况,用避暗试验测定各组大鼠的学习记忆能力,采用Western blot和RT-PCR方法检测各组大鼠海马Uch-L1蛋白及其mRNA的表达水平。结果ZD组血浆锌含量及碱性磷酸酶活性均显著低于PF组和ZA组;ZD组大鼠在避暗试验中的进洞潜伏期显著低于PF组和ZA组;与PF组和ZA组相比,ZD组大鼠海马Uch-L1及其mRNA表达水平明显降低。结论缺锌可下调大鼠海马Uch-L1表达水平。     

Studies of marginal zinc deprivation in rhesus monkeys: II. Pregnancy outcome

A marginal state of zinc deficiency was induced in the pregnant nonhuman primate, Macaca mulatta, by feeding a diet containing 4 ppm zinc beginning at conception. Pregnancy outcome of marginally zinc-deficient monkeys (ZD) was compared to both pair-fed (PF) and ad libitum fed (AL) control animals (100 ppm zinc). Stillbirths, abortions, and delivery complications were more frequent in both ZD and PF dams than in AL controls; no malformations were detected (maternal plasma zinc was normal during organogenesis). Male ZD neonates weighed significantly less than same sex controls; also, in relation to colony norms, 7/8 ZD males, 2/8 ZD females, and 1/10 PF controls were of low birth weight. Further, plasma zinc and iron levels were lower in ZD neonates than in AL and PF controls. ZD neonates also had reduced muscle tonus. Birth weight and maternal plasma zinc concentration were negatively correlated in ZD group but positively correlated in AL and PF groups. Indeed, maternal plasma zinc concentration alone did not identify a state of zinc deficiency which impaired fetal growth in monkeys.     

The cognitive impairment induced by zinc deficiency in rats aged 0∼2 months related to BDNF DNA methylation changes in the hippocampus

Objective: This study was carried out to understand the effects of zinc deficiency in rats aged 0～2 months on learning and memory, and the brain-derived neurotrophic factor (BDNF) gene methylation status in the hippocampus.

Methods: The lactating mother rats were randomly divided into three groups (n?=?12): zinc-adequate group (ZA: zinc 30?mg/kg diet), zinc-deprived group (ZD: zinc 1?mg/kg diet), and a pair-fed group (PF: zinc 30?mg/kg diet), in which the rats were pair-fed to those in the ZD group. After weaning (on day 23), offspring were fed the same diets as their mothers. After 37 days, the zinc concentrations in the plasma and hippocampus were measured, and the behavioral function of the offspring rats was measured using the passive avoidance performance test. We then assessed the DNA methylation patterns of the exon IX of BDNF by methylation-specific quantitative real-time PCR and the mRNA expression of BDNF in the hippocampus by RT-PCR.

Results: Compared with the ZA and PF groups, rats in the ZD group had shorter latency period, lower zinc concentrations in the plasma and hippocampus (P?Conclusion: The learning and memory damage in offspring may be a result of the epigenetic changes of the BDNF genes in response to the zinc-deficient diet during 0～2 month period. Furthermore, this work supports the speculative notion that altered DNA methylation of BDNF in the hippocampus is one of the main causes of cognitive impairment by zinc deficiency.     

锌对免疫器官的影响

通过建立大鼠缺锌（ＺＤ）、高锌（ＺＥ）模型，研究锌对免疫器官——骨髓、胸腺、脾脏的影响。结果表明：（１）ＺＤ、ＺＥ组体重、体重增长值、饲料效价均非常显著地低于配对（ＰＦ）组和自由喂养（ＡＬ）组，缺锌补锌（ＺＤ＋ＡＬ）组达正常水平。（２）ＺＤ组血清、毛发、股骨、肝脏锌均非常显著地低于ＰＦ、ＡＬ组，而ＺＥ组则相反，ＺＤ＋ＡＬ组达正常水平。（３）ＺＤ、ＺＥ组的胸腺重量、胸腺指数、胸腺肽量和胸腺活性均非常显著地低于ＰＦ、ＡＬ组，ＺＤ＋ＡＬ组达正常水平。（４）ＺＤ、ＺＥ组脾脏重量、脾脏指数均非常显著地低于ＰＦ、ＡＬ组，ＺＤ＋ＡＬ组达正常水平。（５）ＺＤ、ＺＥ组骨髓细胞３Ｈ一ＴｄＲ掺入率和外周血白细胞总数显著下降，其中尤以淋巴细胞减少为着。（６）骨髓细胞、脾脏淋巴细胞周期显示ＺＤ、ＺＥ组静止期细胞明显增高，而增殖期细胞下降，与ＰＦ、ＡＬ组间差别非常显著。以上结果提示，适量锌有促进免疫器官——骨髓、胸腺、脾脏发育和功能活动的作用。而缺锌和高锌则抑制免疫器官的发育和免疫细胞的功能。     

缺锌对胸腺和脾脏细胞增殖周期DNA及蛋白质含量的影响

通过建立大鼠缺锌（ＺＤ）模型，采用流式细胞术，研究缺锌对胸腺、脾脏细胞增殖周期、ＤＮＡ及蛋白质含量的影响。结果表明：（１）ＺＤ组的最终体重、体重增长值、饲料效价、以及血清、毛发、股骨锌均非常显著地低于缺锌对喂（ＰＦ）组。（２）ＺＤ组胸腺、脾细胞的增殖指数和Ｇ＿２＋Ｍ期细胞的百分率非常显著地低于ＰＦ组；胸腺、脾脏的Ｇ０／Ｇ＿１期细胞百分率却非常显著地高于ＰＦ组。（３）ＺＤ组胸腺、脾脏细胞的ＤＮＡ含量、ＤＮＡ指数、蛋白质含量、蛋白质指数显著低于ＰＦ组。缺锌时，ＤＮＡ复制和蛋白质合成受到抑制，致使细胞停滞于Ｇ０／Ｇ＿１期，仅少量进入Ｓ期和Ｇ＿２＋Ｍ期、使增殖指数减低。     

The effect of zinc deficiency on prostaglandin synthesis in rat testes

The effect of zinc deficiency on prostaglandin synthesis in rat testes was determined by feeding three groups of rats egg white-based semipurified diets. One group (ZD) was fed a zinc-deficient diet and two control groups were pair-fed (PF) or fed ad libitum (AL) a zinc-sufficient diet. The concentration (nanograms/gram) of the prostacyclin metabolite, 6-keto-prostaglandin-F1 alpha (6-keto-PGF1 alpha), in the tunica homogenate was significantly lower in ZD than in PF and AL groups. However, there was no difference when 6-keto-PGF1 alpha concentration was expressed as nanograms/milligrams of tunica protein. Tunica PGE2 concentrations (nanograms/gram) were not significantly altered by zinc deficiency. Concentrations of prostaglandins (PGs) in testis parenchyma were slightly higher in ZD probably as a result of increased levels of the precursor, arachidonic acid (AA). There was a highly significant correlation between PGE2 and AA in parenchyma phospholipids. PG synthesis was much greater in the tunica than in the parenchyma and prostacyclin appeared to be the major PG synthesized in both the tunica and parenchyma. It was concluded that PG synthesis is altered in the testes of zinc-deficient rats probably due to changes in concentrations of protein in the tunica and AA levels in parenchyma lipids.     

缺锌对生长大鼠学习记忆功能及生长状况的影响

目的 :　研究缺锌对大鼠生长、学习和记忆功能的影响。方法 :　进行了三系列实验 ,第 1、2系列分组均为缺锌组 (ZD)、对喂组 (PF)和缺锌补锌组 (ZS) ,但第 1系列饲养期为 35d,缺锌补锌组缺锌 2 1 d后补锌 ;第 2系列饲养期 2 8d;第 3系列分组为缺锌组、对喂组和自由采食组(AL) ,饲养期 2 8d,全程观察生长过程 ,定期称重 ,并于实验结束前 1 w内用避暗法测定各组大鼠的学习和记忆功能。结果 :　三次实验均表明 ,ZD组大鼠生长、学习和记忆功能降低 ,而补锌后 ,则能逆转上述状况。结论 :　锌不仅影响生长 ,且与学习和记忆等脑的高级功能有关     

Effect of zinc deficiency on appetite and free amino acid concentrations in rat brain

Brain amino acids were measured in 30-day-old male Long-Evans rats subsequent to feeding a 20% egg white biotin-enriched zinc-deficient diet for 9 days. The zinc-deficient (ZD) group was given distilled deionized water. Zinc-supplemented control groups included pair-fed (PF), ad libitum-fed (AL) and ad libitum-fed, overnight fasted (OF) animals. Brain tyrosine concentrations and related amino acid ratios tended to be higher when food was consumed in all groups. Brain tryptophan concentrations and a brain amino acid ratio (glycine + serine + glutamine + taurine:leucine + isoleucine + valine + methionine) were not related to food intake in ZD rats in contrast to zinc-adequate controls. Also the brain ratio of tryptophan to the sum of large neutral amino acids minus tryptophan was not related to food intake in the ZD and AL-OF groups in contrast to the PF group. There were some differences in brain amino acid concentrations between ZD rats and the control groups; however, the pattern of the brain amino acids in ZD rats did not suggest that food intake was directly influenced by them.     

Zinc deficiency suppresses the development of oral tolerance in rats

Oral tolerance is a specific immune unresponsiveness to food antigens to prevent hypersensitivity reactions. We investigated whether zinc deficiency affects oral tolerance. Rats were fed a control (C) or zinc-deficient (ZD) diet, or pair-fed (PF) to ZD rats for 28 d. Beginning on d 7, rats were administered ovalbumin (OVA) orally to induce tolerance, or PBS 3 times/wk, and were then immunized by OVA injection. The proliferation of mesenteric lymph node (MLN) and spleen lymphocytes after in vitro OVA stimulation and the delayed-type hypersensitivity were higher in OVA-fed ZD than in OVA-fed C rats and not different between OVA- and PBS-fed ZD rats, indicating a suppression of tolerance. Lymphocyte proliferation did not differ between PF and C rats. Expressions of cytokines involved in oral tolerance, i.e., interleukin (IL)-4, IL-10 and transforming growth factor-beta, were higher in OVA- than in PBS-fed C rats, but not in ZD rats. Apoptosis was higher in OVA- than in PBS-fed C rats but not different between OVA- and PBS-fed ZD rats. Inflammation and ulcerations that were not present in ZD rats on d 7 (ZD(7)) developed in OVA- or PBS-fed ZD rats. Compared with ZD(7) rats, tumor necrosis factor-alpha and cytokine-induced neutrophil chemoattractant were higher in OVA- and PBS-fed ZD rats, whereas interferon-gamma increased only in OVA-fed ZD rats. In conclusion, zinc deficiency suppresses oral tolerance through dysregulation of cytokine expression and lack of antigen-specific clonal deletion. We suggest that abrogation of tolerance may lead to development of mucosal inflammation and damage.     

锌缺乏对生长期雄性大鼠海马泛素C末端水解酶L1表达的影响

[目的]观察缺锌对生长期大鼠海马泛素C末端水解酶L1(UCH-L1)表达的影响。[方法]将SD大鼠随机分为正常组、缺锌配喂组和缺锌组,正常组喂饲常锌饲料(32.5mg/kg),缺锌配喂组喂饲高锌饲料(73.5mg/kg),缺锌组喂饲缺锌饲料(1.2mg/kg)。饲养4周后处死动物,取海马组织,RT-PCR法检测UCH-L1mRNA的表达水平,Westernblot法检测UCH-L1蛋白的表达水平。[结果]与正常组和缺锌配喂组比较,缺锌大鼠海马中UCH-L1mRNA和蛋白的表达水平均显著下调。[结论]缺锌大鼠海马UCH-L1的表达异常,可能是缺锌导致认知损伤的重要机制之一。     

Zinc status affects neurotransmitter activity in the paraventricular nucleus of rats

Alterations in neurochemical activity in the paraventricular nucleus (PVN) of the hypothalamus may account for decreased intake of zinc-deficient diets. Male Sprague-Dawley rats were fed zinc-deficient (ZD) or zinc-adequate (ZA) diet for 14 d before samples of extracellular fluid in the PVN were collected by microdialysis or push-pull perfusion. A third set of rats was pair-fed (PF) an amount of ZA diet equal to the intake of ZD rats. Samples were collected over a 2-h period spanning the transition from light to dark. All rats then consumed the zinc adequate diet ad libitum for 3 d before a second set of samples was collected. The increase in extracellular norepineprhrine (NE) during h 1 of the dark period to 147 +/- 13% of baseline (P < 0.05) was apparent only in ZA rats at d 14. After the 3-d repletion period, the increase in NE at dark onset occurred in all three groups. An increase in extracellular neuropeptide Y (NPY) at dark onset to 174 +/- 32% of baseline in rats fed ZA (P < 0.01) was measured in all three groups at both d 14 and 17. Basal NPY concentrations were significantly elevated in PF rats on d 14 (7.45 +/- 2.01 vs. 0.58 +/- 0.23 pmol/L, P = 0.01) and returned to ZA levels by d 17. The activities of the NE and NPY systems in the PVN were altered in rats fed a zinc-deficient diet; however, it is unclear whether the disruption in the NE and NPY neural systems in the PVN results in the altered feeding behavior accompanying zinc deficiency.     

Effects of isolated zinc deficiency on the composition of skeletal muscle, liver and bone during growth in rats

We investigated the effects of zinc deficiency on body composition by using intragastric force-feeding to obviate decreased food intake and altered eating patterns. Weanling male Sprague-Dawley rats were fed a purified zinc-deficient diet: the ad libitum-fed control group (AL; eight rats) was given powdered diet and water containing 25 ppm zinc; the zinc-replete group (ZN; nine rats) was force-fed a diet blended with water containing zinc in an amount of equal caloric intake to the AL group and allowed access to water containing zinc. The zinc intake of ZN rats was approximately twice that of AL rats based on water intake. The zinc-deficient group (ZD; 13 rats) was fed similarly to the ZN group except deionized water was used for diet preparation and drinking water. After 8 d, body and muscle weight were lower in the ZD group than in the ZN group. Femur weights were similar in the two groups. Serum, liver and femur zinc concentrations were 85, 22 and 42% lower, respectively, in the ZD group than in the ZN group. Serum glucose, relative liver weight, liver glycogen and liver lipids were higher, but muscle and liver DNA were lower in the ZD group than in control groups.     

缺锌及补锌对大鼠甲状腺激素的影响

目的了解锌缺乏及补锌对大鼠甲状腺激素的影响。方法将出生后断乳1周的SD大鼠随机分为缺锌组、配喂组、对照组、补锌组和高锌组,缺锌组、对照组、高锌组分别用缺锌饲料(Zn含量<1mg/kg),常锌饲料(Zn含量为50mg/kg)和高锌饲料(Zn含量为150mg/kg)喂养8周,补锌组用缺锌饲料喂养3周后改用高锌饲料喂养5周,配喂组用常锌饲料喂养,给料量按缺锌组前一天实际进食量添加。8周后处死,用极谱法测定血清中锌的含量,用放射免疫法测定血清中FT3、FT4的含量。结果缺锌使大鼠血清中锌含量显著降低,血清中FT3含量下降,补锌后恢复正常,缺锌对FT4无影响。结论缺锌引起甲状腺激素FT3下降,而FT4不受影响。