Differential effect of protein and zinc deficiencies on lymphokine activity in BCG-vaccinated guinea pigs

Pathogen-free guinea pigs maintained on isocaloric, purified low protein (LP), low zinc (LZ) and control (C) diets and commercial chow (Ch) were vaccinated with viable Mycobacteriumbovis BCG and sacrificed 4, 5, and 6 weeks later. Both groups of malnourished animals showed weight loss and zinc-deficient guinea pigs had reduced plasma zinc levels. Serum proteins and albumin levels were reduced in LP guinea pigs. Animals on LP and LZ diets showed significantly impaired delayed hypersensitivity to dinitrochlorobenzene and tuberculin when compared to animals consuming the C and the CH regimen. The ability of peritoneal exudate cells to produce macrophage migration inhibition factor (MIF) when stimulated with PPD invitro was diminished in animals maintained on the LZ diet for more than 5 weeks, but was unaffected by protein deficiency. Reduced capacity to produce functional lymphokines may contribute to skin test anergy in chronic zinc deficiency, but does not explain loss of delayed hypersensitivity in protein-deprived guinea pigs.     

Interference in the development of a secondary immune response in mice by zinc deprivation: persistence of effects

The purpose of this study was to determine the effects of a moderate period of zinc deficiency on the secondary responses of mice primed with antigen prior to nutritional insufficiency. Adult A/J mice were primed with sheep red blood cells (SRBC) 2 weeks prior to being placed on zinc-deficient, zinc-adequate or intake-restricted diets. After 28 days some of the mice in each treatment group were given a second injection of SRBC. Deficient mice could produce only 43% as many IgG anti-SRBC plaque-forming cells (PFC) per spleen as could the zinc-adequate or restricted-fed mice. To compare the secondary response of cells from each dietary group in a uniform environment, additional mice were killed as a source of primed splenocyte for transfer to irradiated hosts. Compared to controls, splenocytes from deficient mice gave suboptimal secondary responses even in normal irradiated hosts. Finally, the remaining mice were provided with zinc-adequate diet for a period of 4 weeks to allow for repair of the memory response, but it was only partially restored by this means. The data suggest that zinc deficiency may have destroyed a substantial portion of SRBC memory cells.     

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.     

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。     

Relationship between serum zinc level and immunocompetence in protein-deficient and well-nourished weanling mice

Two experiments were performed in which three-week-old male and female CBA/J mice were fed adlibitum for two weeks either a control diet (18.6% protein) containing adequate levels of all nutrients or a lowprotein diet (Experiment 1: 1.6%; Experiment 2: 0.6%) adequate in all other nutrients. Two thymus-dependent primary immune responses to sheep red blood cells (SRBC), viz. the antibody (hemagglutinin) response and the low-dose delayed hypersensitivity response, were tested in each experiment. Mice fed 1.6% protein maintained weaning weight, but exhibited low thymic and splenic indices (weight relative to body weight), low serum protein levels and low serum zinc levels. These animals, however, displayed normal immune responses to SRBC. Mice fed 0.6% protein lost about 15–20% of their initial (weaning) weight during the 14-day experiment, and exhibited low thymic and splenic indices, low serum protein levels and low serum zinc levels. Both the antibody response and the delayed hypersensitivity reaction were depressed in these animals. Subcutaneous zinc injections raised the serum zinc level to nearnormal in mice fed 0.6% protein, but did not influence either immune response examined. By contrast parenterally administered zinc reduced the antibody response of well nourished mice to about 15% of normal, although the delayed hypersensitivity response was not affected in this group of animals. A negative correlation (R=?0.72, P<0.02) was found between serum zinc level and hemagglutinin titer in the zinc-injected, well-nourished animals. The results suggest that thymus-dependent immune responses are highly resistant to the adverse effects of protein deficiency, but do not support the hypothesis (proposed by others) that secondary zinc deficiency is a primary underlying cause of the immunodepression which occurs in severe protein deficiency. In addition, it appears that zinc supplements can depress some immune responses of well-nourished individuals if the quantities administered overwhelm the mechanism(s) regulating serum zinc level.     

Long-term zinc deficiency decreases taste sensitivity in rats

The effects of zinc deficiency on taste sensitivity were examined in rats by recording the electrophysiological responses of the chorda tympani (CT) nerve and by use of a preference test. Male 4-wk-old Sprague-Dawley 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. A fourth group was pair-fed the zinc-sufficient diet (with respect to the zinc-deficient rats). A two-bottle preference test using 0.15 mol/L NaCl and water revealed that NaCl preference was greater in the zinc-deficient and low zinc groups than in the control groups (zinc-sufficient and pair-fed) after 4 d of feeding. In the case of quinine hydrochloride solution (0.01 mmol/L), the preference was greater in zinc-deficient rats than in the other groups after 9 d, and the low zinc rats never showed a preference. Electrophysiological recording indicated that in the zinc-deficient rats, the CT nerve response to 0.20 mol/L NaCl was significantly less than that in the control rats after 21 d of feeding. In the low zinc rats, this response was significantly less than in the control rats after 35 d. The responses to quinine hydrochloride (0.02 mol/L), L-glutamic acid, HCl (0.01 mol/L) and NH(4)Cl (0.25 mol/L) in the zinc-deficient rats were not significantly reduced until d 42. These findings suggest that long-term zinc deficiency decreases taste sensitivity at the level of the CT nerve and that the change in NaCl preference due to zinc deficiency occurs before any change in NaCl taste sensitivity.     

Effect of zinc status on salivary zinc concentrations in the rat.

Three experiments were done to determine whether salivary zinc concentration is a more sensitive indicator of zinc status than plasma zinc. Weanling male rats fed a low zinc (less than 1 ppm) diet for 5 weeks with or without zinc (100 ppm) in the drinking water had salivary zinc concentration of 0.19, 0.16, and 0.20 microgram/ml for the zinc-deficient, zinc-supplemented restricted-intake, and zinc-supplemented ad libitum-fed groups, respectively. Combined values for male and female rats after 4 weeks of the same treatments in experiment 2 were 0.60, 1.2 and 0.44 microgram/ml. Saliva collected on day 22 of pregnancy contained 0.30 and 0.24 microgram/ml from zinc-supplemented and zinc-deficient rats, respectively. Salivary zinc concentrations in the deficient rats did not differ from those of the zinc-supplemented ad libitum-fed controls in any of the experiments. Salivary zinc concentration in the zinc-supplemented restricted-intake group in experiment 2 was significantly higher than that in the other two groups. Decreases in serum, bone, and fetal zinc concentrations indicated that the rats were definitely zinc-deficient. Since zinc concentration of mixed saliva in the rat was not decreased by even a severe zinc deficiency, salivary zinc does not appear to be as good an indicator of zinc status as plasma zinc.     

锌缺乏对生长期大鼠免疫细胞凋亡的影响

目的: 观察饲料锌缺乏对生长期大鼠免疫细胞凋亡的影响,并探讨其分子机制。方法: 通过喂食锌含量不同的饲料,构建生长期缺锌大鼠模型;TUNEL方法原位检测胸腺、脾脏组织淋巴细胞凋亡,半定量RT-PCR方法检测一对凋亡调控基因bcl-2/bax mRNA的表达。结果: 与锌充足组(ZA)和配饲组(PF)相比,缺锌组(ZD)大鼠胸腺、脾脏淋巴细胞凋亡增多,促凋亡基因bax mRNA表达增高,补锌后上述改变可得到恢复。结论: 饲料锌缺乏导致发育中和成熟的淋巴细胞凋亡增多,凋亡调控基因bcl-2/bax表达失衡是重要机制之一。     

缺锌并补锌对大鼠睾丸及血清睾酮的影响

目的　为了解锌缺乏及补锌对大鼠睾丸的重量及血清睾酮的影响。　方法　将出生后断乳一周的SD大鼠随机分为缺锌组、配喂组、对照组、补锌组和高锌组五组 ,缺锌组、对照组和高锌组分别用缺锌饲料 (锌含量 <1mg/kg)、常锌饲料 (锌含量为 5 0mg/kg)和高锌饲料 (锌含量为 15 0mg/kg)喂养 8周 ,补锌组用缺锌饲料喂养三周后改用高锌饲料喂养五周 ,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含量 ,用原子吸收分光光度法测定睾丸中锌含量 ,采用双抗体放射免疫分析法测定血清中睾酮的含量。　结果　缺锌组大鼠睾丸及血清中锌含量降低 ,睾丸重量减轻。血清中睾酮含量下降 ,缺锌大鼠补锌后可恢复正常。　结论　说明锌缺乏直接影响睾丸及血清中锌的水平 ,从而影响大鼠睾丸的发育及睾酮的分泌与合成。     

Effects of prostaglandin modifiers and zinc deficiency on possibly related functions in rats

Experiments were conducted to investigate the role of prostaglandins (PG) in zinc absorption and biological functions (food intake and weight gain, alkaline phosphatase activity, T-cell-mediated immune response). PG levels were modified by administering an inhibitor of their synthesis, aspirin or indomethacin in the diet. Zinc level was modified by controlling the dietary concentration. Weanling rats were fed the assigned diets for 1 month after which they were anesthetized with ether. Samples of blood, gut contents and mucosa, liver, lung and tibia were collected for zinc, PG, lymphocyte stimulation with T-cell mitogen, and alkaline phosphatase assays. There was more than 50% inhibition of PG synthesis by indomethacin and aspirin. This inhibition of PG synthesis, however, did not affect the zinc status of the rats as measured by general appearance, food intake, weight gain, organ weight, zinc concentration in different organs, serum alkaline phosphatase activity, and cell-mediated immune response to T-cell mitogens. It is concluded that under physiological conditions inhibitors of PG synthesis do not alter these zinc metabolic functions.     

Actions and interactions of thyroid hormone and zinc status in growing rats

Both thyroid hormone (triiodo-L-thyronine, T3) and zinc play important roles in growth and development. The T3 receptor is thought to require zinc to adopt its biologically active conformation. Some of the effects of zinc deficiency, therefore, may be due to loss of zinc from the T3 receptor and impairment of T3 action. This possibility was investigated in growing rats by examining the effects of hypothyroidism and hyperthyroidism in zinc-deficient, pair-fed and control rats. Measurement of serum zinc and T3 confirmed the efficacy of the treatments. Zinc deficiency and hypothyroidism resulted in lower food intake and growth failure, but no interaction was observed between the two treatments. Individual tissue weights were influenced by thyroid status as expected, regardless of zinc status. Both dietary and hormonal treatments influenced serum insulin-like growth factor (IGF)-I in an interactive manner. IGF-I was reduced to a greater extent in zinc-deficient than in pair-fed rats compared with controls. Both hypothyroidism and hyperthyroidism reduced serum IGF-I, and a greater reduction due to hyperthyroidism was apparent in zinc-deficient rats. IGF binding proteins were also influenced by diet and thyroid status. The hepatic expression of mRNA S14 was assessed as a direct index of the nuclear action of T3, but its response was not influenced by dietary treatment. Although confirming the role of both T3 and zinc in the regulation of growth and the somatotrophic axis, the growth failure of zinc deficiency does not appear to be due to impaired T3 function.     

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...     

Effects of dietary protein levels on body composition of zinc-deficient rats

This study examined why decreased protein intake retards zinc deficiency in zinc-deficient rats. Rats were freely provided zinc-deficient diets with either 10 or 20% protein. Experimental groups consisted of five rats that were fed experimental diets for 0, 3, 4, 12 and 25 d in Experiment 1. The body protein content in rats fed the 10% protein diet was similar to those fed the 20% protein diet for the duration of the experiment. The body zinc content in both dietary groups slowly decreased in a similar manner. Eventually, the body zinc/protein ratio in the 10% protein diet group decreased more slowly than that in the 20% protein diet group. Ingestion of the 10% protein diet also reduced the zinc/protein ratio in bone more slowly compared with that of the 20% protein diet, under zinc-deficient conditions, at 12 d in Experiment 2. However, there was no difference in the zinc/protein ratio of carcass total soft tissue between the two zinc-deficient groups. Decreased protein intake eventually slowed the reduction in both the body and bone zinc/protein ratios in zinc-deficient rats, resulting in retardation of zinc deficiency.     

Alterations in immune function in rats caused by dietary lipotrope deficiency: effect of age

Weanling male Sprague-Dawley rats were maintained on a control (C), folacin-deficient (F) or marginal methionine-choline diet (M/C) for 3 weeks, 3 months or 12 months. The immunocompetence of the animals was determined by in vivo (response to infection with salmonella typhimurium) and in vitro (lymphocyte transformation assay) methods. It was found that young animals were most sensitive to dietary lipotrope deficiency, and the in vivo response to bacterial infection did not always correlate with in vitro assessment of immune function. Histopathologic examination of spleens from S. typhimurium-infected rats maintained for 3 weeks on the experimental diets showed an overall decreased cellularity especially in the follicular areas, compared to controls. No differences were seen in the spleens of infected animals at later time points. A short-term (3-week) lipotrope deficiency resulted in a depressed lymphocyte transformation response to concanavalin A (Con A) in the spleen, thymus and lymph nodes; to phytohemagglutinin A (PHA) in the spleen and lymph nodes only. After 3 months on the F or M/C diets, a depressed Con A-induced transformation response was still seen in the spleen, but the normal aging-induced immunosuppression resulted in a low response in all animals, with few significant differences existing among groups.     

Gestational zinc requirement of the A/J mouse: Effects of a marginal zinc deficiency on in utero B-cell development

A series of studies were initiated to define the effects of suboptimal zinc intake on in utero development of the immune system using the A/J mouse. Dams were fed a biotin-fortified egg white diet containing 1.3, 2.7, 3.8, 6.2, 10 or 30 μg Zn/g (control) from days 0 to 18 of gestation. It was found that a dietary zinc level of 10 μg Zn/g was adequate for gestation. Dams fed 3.8 μg Zn/g had a modest decrease in weight gain and serum zinc levels; by day 18 fetal body weights were 86% the weight of control fetuses. Thus, the 3.8 μg Zn/g diet was judged to be marginal and was subsequently used to study B-cell development in the fetal liver. Day 18 fetal liver cells (FLC) were prepared from groups receiving adequate (30 μg Zn/g), adequate but restricted-fed (30 μg Zn/g) and marginal levels (3.8 μg Zn/g) of dietary zinc for adoptive transfer to normal, irradiated adult hosts. In response to a T-cell independent antigen (TI), the recipients which received FLC from the marginal or restricted-fed groups produced 49% and 90% respectively as many antibody producing cells per spleen as recipients which received FLC from normal fetuses. The results indicate that B-cell development in utero was significantly altered by a marginal zinc deficiency.     

The absorption of pteroylpolyglutamate and intestinal pteroylpolygammaglutamyl hydrolase activity in zinc-deficient rats

The effect of dietary zinc deficiency on pteroylpolygammaglutamyl hydrolase (folate hydrolase) activity and on pteroylpolyglutamate absorption was studied in rats. Three groups of male Sprague-Dawley rats (zinc-deficient, restricted-fed and ad libitum-fed controls) were fed a semipurified 25% egg white protein diet. The zinc-deficient group received 0.7 mg zinc/kg diet, whereas restricted-fed and ad libitum-fed control groups received 106 mg zinc/kg diet. After 6 wk of feeding, intestinal mucosal folate hydrolase activity was determined, and the absorption of pteryl-U[14C]glutamylhexaglutamic acid [(14C]PteGlu7) and [3H]pteroylglutamic acid [(3H]PteGlu) was measured after intragastric administration. The intestinal mucosal folate hydrolase activity of zinc-deficient rats was not significantly reduced compared with two control groups. No significant differences in the absorption of [14C]PteGlu7 and [3H]PteGlu were found among the three groups. These results indicate that intestinal folate hydrolase is not zinc dependent in rats and the intestinal absorption of pteroylpolyglutamate is not reduced in zinc-deficient rats.     

The teratogenic effect of zinc deficiency and accompanying feeding patterns in mice

The effect of zinc deficiency on fetal development in rats is well established, as also is the importance of the accompanying feeding/fasting cycle on the severity of the zinc-related dysmorphology. Little is known concerning the teratogenesis of zinc deficiency in mice and nothing has been reported with respect to the feeding pattern in this species when fed a zinc-deficient diet. The present studies with pregnant mice (C57BL/6J) revealed them to be acutely sensitive to dietary zinc restriction, with the result that total loss of offspring occurred when the diet contained less than 5 ppm of zinc. Severe teratogenesis accompanied intakes of between 5 and 10 ppm of zinc, but in contrast to rats, no cyclical feeding pattern was evident in mice receiving a zinc-deficient diet, nor was food intake depressed when expressed on a body weight basis. Tissue zinc levels in mice responded to dietary zinc restriction in a manner similar to that reported for rats, with plasma and bone zinc levels being especially sensitive to the zinc intake.     

L-threonine supplementation increases the amplitude of the feed intake cycle of rats fed a low-protein zinc-deficient diet

Rats fed a Zn-deficient diet show characteristic variations in feed intake. These variations were followed by means of a personal computer. The specific feed intake patterns in rats fed a zinc-deficient diet before and after supplementation with protein and several essential amino acids were determined. The high-protein diet decreased the amplitude of feed intake under zinc deficiency, probably because of a decrease in sensitivity to the deficiency. Furthermore, the zinc-deficient diet was supplemented with essential amino acids, and of them L-threonine showed the most marked effect on the increased variability of feed intake.     

Zinc-deficient rats have fewer recent thymic emigrant (CD90+) T lymphocytes in spleen and blood

It has been hypothesized that increased expression of the signaling protein p56(lck) disrupts maturation of T lymphocytes, leading to the lymphopenia associated with dietary zinc deficiency and malnutrition. Our objective was to examine p56(lck) protein levels, flow cytometric markers of T cell development (CD4, CD8, TCRalphabeta, TCRgammadelta and CD90) and absolute cell numbers in thymus, spleen and blood of zinc-deficient (ZD), diet-restricted (DR) and control (CTL) rats. Recent thymic emigrant (CD90+) T lymphocytes were also investigated after dietary repletion. P56(lck) protein levels were one- to twofold greater in thymocytes than splenocytes, and ZD rats had more thymocyte p56(lck) protein than CTL rats. In the thymus and blood, the proportions of T lymphocyte subpopulations (CD4-CD8-, CD4+CD8+ and CD4+CD- or CD4-CD8+) were unchanged, except for a higher percentage of TCRalphabeta+CD-CD8+ thymocytes in ZD rats. The 15-29% fewer CD90+ T cells in the blood and spleen of ZD rats were reversed after dietary repletion for 7 and 23 d, respectively. In summary, T-cell numbers were proportional to thymus and spleen weights and unaltered per unit blood volume, despite elevated thymocyte p56(lck) protein in ZD rats. In zinc deficiency, the decreased percentages of CD90+ cells in the blood and spleen could adversely affect the T-cell repertoire.     

Zinc-deficient rats are insensitive to glucoprivation caused by 2-deoxy-D-glucose

Three-choice macronutrient intake studies indicate that zinc-deficient (Zn-) rats selectively decrease intake of carbohydrate. Because glucoprivic stimuli increase food intake and selection for carbohydrate, the ability of Zn- rats to respond to glucoprivation induced by 2-deoxy-D-glucose (2-DG) was tested. Rats were fed a Zn-adequate (Zn+) or Zn- diet. In part 1, rats were challenged with 0, 250, or 400 mg 2-DG/kg BW (i.p.) after zinc deficiency was established. In part 2, rats received saline or 2-DG while zinc deficiency was being induced and then after deficiency was established. Food intake was increased after injection of 2-DG to Zn+ rats; however, food intake was not higher after 2-DG administration to Zn- rats. A dose-response test for 2-DG further confirmed these results. In part 2, it was found that Zn- rats lose the response to 2-DG administration when zinc deficiency-induced anorexia begins, after 3 days of consuming a zinc-deficient diet. It appears that the ability to sense blood glucose concentrations may be impaired during zinc deficiency, and this impairment could be a part of the anorexia that develops during zinc deficiency in the rat.