共查询到20条相似文献,搜索用时 15 毫秒
1.
Jan Wensink Clement H. Paays Cornelis J. A. van den Hamer 《Biological trace element research》1987,14(1-2):127-141
After a single injection,65Zn is slowly taken up by the brain of the rat to a maximum after 7 d, followed by a turnover phase, with a half-time of about
3 wk. In the brain of rats on a zinc-deficient diet, the65Zn content in the brain continued to increase up to 30 d after the injection.
The uptake and turnover phases in six different subcellular fractions of the brain showed a pattern similar to that of the
whole brain in both the control and zinc-deficient rats. There was no internal redistribution of65Zn in the brain under conditions of progressive zinc deficiency.
The results are discussed in a model for zinc homeostasis in the brain. 相似文献
2.
Zinc is essential for normal growth, development and brain function although little is known about brain zinc homeostasis. Therefore, in this investigation we have studied65Zn uptake from blood into brain and other tissues and have measured the blood-brain barrier permeability to65Zn in the anaesthetized rat in vivo. Adult male Wistar within the weight range 500–600 g were used.65ZnCl2 and [125I]albumin, the latter serving as a vascular marker, were injected in a bolus of normal saline I.V. Sequential arterial blood samples were taken during experiments that lasted between 5 min and 5 hr. At termination, samples from the liver, spleen, pancreas, lung, heart, muscle, kidney, bone, testis, ileum, blood cells, csf, and whole brain were taken and analysed for radio-isotope activity. Data have been analysed by Graphical Analysis which suggests65Zn uptake from blood by all tissues sampled was unidirectional during this experimental period except brain, where at circulation times<30 min,65Zn fluxes were bidirectional. In addition to the blood space, the brain appears to contain a rapidly exchanging compartment(s) for65Zn of about 4 ml/100g which is not csf. 相似文献
3.
This study was designed to determine the effect of zinc on the biological half-lives of 65Zn in whole body and liver and on distribution of 65Zn in different organs of rats following nickel toxicity. Sprague-Dawley (SD) rats received either nickel in the form NiSO4·6H2O at a dose of 800 mg/L in drinking water, zinc in the form of ZnSO4·7H2O at a dose of 227 mg/L in drinking water, and nickel plus zinc or drinking water alone for a total duration of 8 wk. All
of the rats were injected with a tracer dose of 0.37 MBq 65Zn at the end of the treatment period. The effects of different treatments were studied on biological half-lives of 65Zn in whole body and liver and on the distribution of 65Zn in different organs of rats. In the present study, we have noted that nickel treatment to normal rats caused a significant
decrease in the slow component (Tb2) in liver, which improved following zinc supplementation. Nickel administration to normal-diet-fed animals caused significant
lowering in the percentage uptake of 65Zn values in the brain, liver, and intestine. However, the administration of zinc to nickel-treated rats improved the status
of 65Zn in different organs. The Tb2 in the liver and the percentage uptake of 65Zn values elevated following zinc supplementation to nickel-treated rats. 相似文献
4.
The present study was planned to determine the potential of zinc in attenuating the toxicity induced by 131I in rat blood. Female wistar rats were segregated into four main groups. Animals in Group I served as normal controls; Group
II animals were administered a dose of 3.7 Mbq of 131I (carrier free) intraperitoneally, Group III was supplemented with Zinc in the form of ZnSo4.7H2O (227 mg/l drinking water), and Group IV was given a combined treatment of Zinc as well as 131I, in a similar way as was given to Groups IV and II animals, respectively. The effects of different treatments were studied
on various parameters in rat blood including hemoglobin (Hb) levels, % hematocrit, zinc protoporphyrins (ZPP), activities
of enzymes which included aminolevulinic acid dehydratase (δ-ALAD) and Na+ K+ ATPase and uptake of 65Zn in blood. The study revealed an increase in the levels of hemoglobin, % hematocrit, activities of δ-ALAD, Na+ K+ ATPase and uptake of 65Zn, 7 days after the 131I treatment. On the contrary, the levels of ZPP were found to be significantly decreased after 131I treatment. However, zinc treatment to 131I-treated animals significantly attenuated the various biochemical and hematological indices. Moreover, zinc treatment to
the 131I-treated animals could significantly decrease the uptake of 65Zn, which was increased after 131I treatment. Based upon these data, the present study suggests that zinc has the potential to attenuate 131I induced toxicity by restoring the altered hematological indices and biochemical changes. 相似文献
5.
Histidine has been reported to affect body zinc status by increasing urinary zinc excretion. The effects of experimental histidinemia on distribution of65Zn in anesthetized rats were studied. Infusion ofl-histidine at a rate sufficient to raise plasma concentrations to approximately 2mm for 6h starting 48 h after a single intraperitoneal65Zn injection did not alter65Zn activities in a variety of tissues when compared with anesthetized uninfused animals. However, plasma65Zn and erythrocyte65Zn were decreased, and liver65Zn was increased. If65Zn was injected intravenously during histidine infusion, net accumulation of zinc by some tissues was increased, but uptake by others was reduced relative to uninfused animals. In all cases, however, uptake expressed relative to plasma65Zn levels was increased when allowance was made for the more rapid fall in plasma65Zn during histidine infusion. Similar infusions ofd-histidine produced quantitatively similar effects. Since enzymatic mechanisms and amino acid carriers would be expected to show stereoselectivity, such processes are unlikely to be involved in the zinc distribution changes described. The possibility of zinc transport by a hitherto unidentified carrier is discussed. These experiments confirm that histidinemia can affect zinc status, but any associated changes in urinary zinc excretion do not seem adequate to account for the tissue changes found. 相似文献
6.
Equivalent uptake of organic and inorganic zinc by monkey kidney fibroblasts, human intestinal epithelial cells, or perfused mouse intestine 总被引:1,自引:0,他引:1
Kathleen T. Beutler Oleh Pankewycz David L. Brautigan 《Biological trace element research》1998,61(1):19-31
Zinc (Zn) is recognized as an essential nutrient, and is added as a supplement to animal and human diets. There are claims
that zinc methionine (ZnMet) forms a stable complex that is preferentially transported into tissues, and this has contributed
to uncertainty about conflicting reports on the bioavailability of various Zn compounds. This study evaluated the cellular
and intestinal uptake of inorganic and organic forms of Zn. Steady-state uptake of65Zn by human intestine epithelial cells, and monkey kidney fibroblasts was not significantly different with zinc chloride (ZnCl2), ZnMet, or zinc propionate (ZnProp) (P > 0.05). Uptake of65Zn from zinc chelated with EDTA was significantly lower (P < 0.01). In live mice,65Zn uptake by perfused intestine and deposition in intestine and liver showed no significant difference between ZnCl2 and ZnMet. Equimolar [65Zn]methionine and zinc[35S]methionine were prepared according to a patented method that yields “ complexed” Zn. Cellular uptake of the radiolabeled
methionine was <0.1% of the radiolabeled Zn from these complexes, indicating separate uptake of the Zn and methionine. Gel
filtration did not distinguish between65Zn in ZnCl2, ZnProp, or reagent ZnMet, though feed-grade ZnMet containing >10% protein did give a higher-mol-wt form of65Zn. Results of this study show equivalent uptake of Zn from inorganic and organic compounds, and support recent feed trials
on Zn bioavailability. 相似文献
7.
The effect of the chronic administration of histidine on the brain zinc level was examined in growing, male Wistar rats. Using
a purified diet, the minimum zinc requirement for normal growth and normal plasma and tissue zinc levels was found to be around
10 ppm. Given this zinc content; the diet was supplemented with 5% and 8% histidine, respectively, or with 10% glycine (as
control). Brain zinc was analyzed by measuring the rate of turnover of65Zn from 2–4 weeks after a single injection of the tracer. Feeding the diet supplemented with 5% histidine caused a small decrease
in the plasma zinc concentration and a slight increase in the rate of turnover of65Zn in the cerebrum and the cerebellum as compared to the control group. The animals fed the diet supplemented with 8% histidine
became severely zinc deficient (as evidenced by a 50% reduction in the plasma zinc content), however, the rate of turnover
of65Zn in all brain regions examined was significantly decreased as compared to the control group. The results indicate that histidine
has no specific complexing action on the brain zinc. 相似文献
8.
J. De Kok C. Van Der Schoot M. Veldhuizen H. Th. Wolterbeek 《Biological trace element research》1993,38(1):13-26
The in vitro uptake of zinc by erythrocytes was measured under near-physiological conditions, using65Zn as a radioactive tracer. Because of the presence of serum albumin—a strong zinc ligand—a low concentration of medium free
zinc was maintained. Under these conditions a high-affinity carrier for zinc transport over the cell membrane was identified.
With human erythrocytes, a Michaelis constant (K
m
) of 0.2 nM with respect to free medium zinc was measured and aV
max
of 4.5 nmoles Zn transported per h/g dry wt. TheK
m
for medium Zn increases when the size of the internal erythrocytic Zn pool is augmented, whereasV
max
remains virtually unchanged. A model to explain this phenomenon is proposed. It is suggested that this phenomenon could underlie
observations, confirmed here, that the in vitro uptake of Zn by animal erythrocytes depends on the Zn status of the animal. 相似文献
9.
Adult lethal milk (lm/lm) mutant mice display increased induction of hepatic metallothionein synthesis compared to wild-type mice following the subcutaneous injection of 40 µmol ZnCl2/kg mouse. At this zinc dose the rate of incorporation of |35S| cysteine into hepatic metallothionein in adult (100-to 230-day-old) lm/lm mice was approximately 2.4-fold greater than the rate of incorporation of isotope in wild-type animals. At a higher zinc dose (160 µmol ZnCl2/kg) the incorporation of |35S| cysteine into hepatic metallothionein was similar in lm/lm and wild-type mice. The altered dose-response to zinc administration was not due to a change in hepatic zinc, copper, or manganese levels, to a difference in 65Zn uptake, or to an alteration in 65Zn bound to differential centrifugation fractions of adult lm/lm liver. 65Zn bound to hepatic metallothionein was, however, increased in aging lm/lm mice with symptomatic skin lesions. 相似文献
10.
W. Jiang P.C. Struik J. Lingna H. van Keulen Z. Ming & T.J. Stomph 《The Annals of applied biology》2007,150(3):383-391
We investigated the uptake and distribution of zinc (Zn) either applied to the roots or to the leaves in rice during grain development. Plants of two aerobic rice cultivars were grown in a nutrient solution with either sufficient Zn or surplus Zn. Root treatment with 1 week‘s supply of both 65Zn and unlabelled Zn was started at flowering or 15 days after flowering (DAF). Foliar treatment with 65Zn applied to the flag leaf or to senescent leaves was carried out at flowering. When 65Zn was applied to roots, plants continued to take up Zn after flowering, even beyond 15 DAF, irrespective of cultivar and Zn nutritional status of the plants. During the 1 week of supply of both 65Zn and unlabelled Zn, which either started at flowering or 15 DAF, the absorbed 65Zn was mainly distributed to roots, stem and grains. Little 65Zn was allocated to the leaves. Following a week of 65Zn supply directly after flowering, under sufficient Zn or surplus Zn, the proportions of total 65Zn uptake allocated to the grains continued to change during grain filling (9–33%). This Zn mainly came from the roots but under sufficient Zn supply also from the stem. With 65Zn applied to leaves (either the flag leaf or the lowest senescent leaf), both cultivars showed similar Zn distribution within the plants. About 45–50% of the 65Zn absorbed was transported out of the 65Zn‐treated leaf. From that Zn, more than 90% was translocated to other vegetative organs; little was partitioned to the panicle parts and even less to the grains. These results suggest that in rice plants grown under sufficient or surplus Zn supply, most of the Zn accumulated in the grains originates from uptake by roots after flowering and not from Zn remobilisation from leaves. 相似文献
11.
Uptake and transport of foliar applied zinc (65Zn) in bread and durum wheat cultivars differing in zinc efficiency 总被引:5,自引:0,他引:5
Using two bread wheat (Triticum aestivum) and two durum wheat (Triticum durum) cultivars differing in zinc (Zn) efficiency, uptake and translocation of foliar-applied 65Zn were studied to characterize the role of Zn nutritional status of plants on the extent of phloem mobility of Zn and to determine the relationship between phloem mobility of Zn and Zn efficiency of the used wheat cultivars. Irrespective of leaf age and Zn nutritional status of plants, all cultivars showed similar Zn uptake rates with application of 65ZnSO4 to leaf strips in a short-term experiment. Also with supply of 65ZnSO4 by immersing the tip (3 cm) of the oldest leaf of intact plants, no differences in Zn uptake were observed among and within both wheat species. Further, Zn nutritional status did not affect total uptake of foliar applied Zn. However, Zn-deficient plants translocated more 65Zn from the treated leaf to the roots and remainder parts of shoots. In Zn-deficient plants about 40% of the total absorbed 65Zn was translocated from the treated leaf to the roots and remainder parts of shoots within 8 days while in Zn-sufficient plants the proportion of the translocated 65Zn of the total absorbed 65Zn was about 25%. Although differences in Zn efficiency existed between the cultivars did not affect the translocation and distribution of 65Zn between roots and shoots. Bread wheats compared to durum wheats, tended to accumulate more 65Zn in shoots and less 65Zn in roots, particularly under Zn-deficient conditions. The results indicate that differences in expression of Zn efficiency between and within durum and bread wheats are not related to translocation or distribution of foliar-applied 65Zn within plants. Differential compartementation of Zn at the cellular levels is discussed as a possible factor determining genotypic variation in Zn efficiency within wheat. 相似文献
12.
Amrita Dutta Matthew Schaller Aime T. Franco Kavitha Sankavaram Bruce J. Grattan Hedley C. Freake 《The Journal of nutritional biochemistry》2010,21(2):162-170
Previous studies in our laboratory have demonstrated that reducing the availability of zinc with the extracellular metal chelator DTPA (diethylenetriaminepentaacetate) enhances, rather than inhibits, the thyroid hormone induction of growth hormone mRNA in GH3 rat anterior pituitary tumor cells. To understand the actions of the chelator on cellular zinc status, we observed the effects of DTPA on 65Zn uptake and retention. DTPA reduced the uptake of 65Zn by GH3 cells from the medium, but when GH3 cells were prelabeled with 65Zn, it resulted in greater retention of the isotope. In primary hepatocytes, DTPA both reduced the uptake of 65Zn from the medium and increased efflux from prelabeled cells. To investigate this difference, we studied the effects of DTPA on radioactive zinc flux in the H4IIE (rat hepatoma), MCF-7 (human breast cancer) and Hs578Bst (nontransformed human mammary) cell lines and in rat primary anterior pituitary cells. DTPA reduced the uptake of 65Zn in all cell lines examined. DTPA increased the retention of 65Zn in prelabeled H4IIE, MCF-7 and Hs578Bst cells but reduced it in primary pituitary cells. Time course experiments showed that 65Zn efflux is shut down rapidly by DTPA in transformed cells, whereas the chelator causes greater efflux from primary hepatocytes over the first 6 h. Experiments with 14C-labeled DTPA confirmed that this chelator does not cross cell membranes, showing that it operates entirely within the medium. Expression of ZnT-1, the efflux transporter, was not affected by DTPA in H4IIE cells. Thus, zinc deprivation enhanced zinc retention in established cell lines but increased efflux from primary cells, perhaps reflecting differing requirements for this mineral. 相似文献
13.
F. Houlbrèque R. Rodolfo-Metalpa R. Jeffree F. Oberh?nsli J.-L. Teyssié F. Boisson K. Al-Trabeen C. Ferrier-Pagès 《Coral reefs (Online)》2012,31(1):101-109
Zinc (Zn) is an essential element for corals. We investigated the effects of ocean acidification on zinc incorporation, photosynthesis,
and gross calcification in the scleractinian coral Stylophora pistillata. Colonies were maintained at normal pHT (8.1) and at two low-pH conditions (7.8 and 7.5) for 5 weeks. Corals were exposed to 65Zn dissolved in seawater to assess uptake rates. After 5 weeks, corals raised at pHT (8.1) exhibited higher 65Zn activity in the coral tissue and skeleton, compared with corals raised at a lower pH. Photosynthesis, photosynthetic efficiency,
and gross calcification, measured by 45Ca incorporation, were however unchanged even at the lowest pH. 相似文献
14.
Isolated rat hepatocytes were used to investigate the uptake of zinc at early exposure times. Hepatocytes were incubated with 65Zn (1–500 μM) and samples were withdrawn at times ranging from 25 s to 60 min. A biphasic pattern of uptake was observed with a rapid first phase of uptake followed by a slower second phase. The relationship between velocity of uptake and substrate concentration for the first phase was nonlinear, while that of the second phase was linear. The presence of 10 μM cadmium produced a decrease in the velocity of uptake of only the first phase. This suggests that the first phase is at least partly carrier mediated, while there is no indication of involvement of a carrier in the second phase. KCN (1 mM) and carbonyl cyanide m-chlorophenylhydrazone (2 μM), did not cause any change in the uptake of 65Zn (1 μM), which suggests that there is no active component in the uptake of zinc. 相似文献
15.
Compartmentation and transport of zinc in barley primary leaves as basic mechanisms involved in zinc tolerance 总被引:11,自引:1,他引:11
The heavy metal zinc was administered to barley seedlings by increasing its concentration in the hydroponic medium. The most dramatic effect was a severe inhibition of root elongation with little effect on root biomass production. The growth of primary leaves was little affected although the zinc content of the primary leaves increased several-fold. A detailed compartment analysis was performed for 10-d-old barley primary leaves. Under low zinc nutrition (2mmol m −3), highest zinc contents were observed in the cytoplasm of mesophyll protoplasts. At inhibitory zinc concentrations in the hydroponic medium (400 μmol m −3), zinc levels dramatically and preferentially increased in the apoplastic space. Elevated zinc levels were also observed in the epidermal cells, and to a lesser extent, in mesophyll vacuoles. The cytoplasmic content of mesophyll protoplasts was unchanged, indicating perfect zinc homeostasis within the leaf. In order to understand the transport mechanisms underlying the steady-state distribution profile, we used 65Zn to conduct uptake experiments with leaves whose lower epidermis had been stripped. The leaves were placed on zinc solutions of varying concentrations containing 65Zn for 5 min to 6 h. After the incubation, the leaves were fractionated into mesophyll and epidermis protoplasts and residue, the latter mainly representing cell wall. Adsorption of Zn to the extracellular matrix was 100 times faster than Zn uptake into the cells. By far the largest portion taken up into the mesophyll protoplasts rapidly appeared in the vacuolar compartment. These results demonstrate the importance of compartmentation and transport as homeostatic mechanisms within the leaves to handle high, possibly toxic, zinc levels in the shoot. 相似文献
16.
C. Sarathambal M. Thangaraju C. Paulraj M. Gomathy 《Indian journal of microbiology》2010,50(1):103-109
Solubilization of insoluble zinc compounds like ZnCO3 and ZnO by G. diazotrophicus was confirmed using radiotracers. The zinc compounds (ZnCO3 and ZnO) were tagged with 65Zn. 65ZnCO3 and 65ZnO was effectively solubilized and the uptake of zn by the plants also more in G. diazotrophicus inoculated treatments compared to the uninoculated treatments. Three types of soils (Zn deficientsterile, Zn deficient-unsterile, and Zn sufficient-sterile) were used in experiment. Among the three soils, Zn deficient-unsterile soil registered maximum zinc solubilization compared to other two soils. This may be due to other soil microorganisms in unsterile soil. Application of ZnO with G. diazotrophicus showed better uptake of the nutrient. 相似文献
17.
Interspecific hybrids of Exacum exhibit variation in the expression of zinc efficiency. This research investigated the genetic basis for this variation and evaluated a series of physiological and morphological traits for their association with zinc efficiency. Chi-square analyses of self-pollinated progeny from both zinc-efficient and zinc-inefficient parents indicate a significant genetic component. One hundred percent of the progeny from the inefficient parent were classified as inefficient, while the progeny from the efficient parent segregated 32% inefficient to 68% efficient. Six plants from each phenotypic class (efficient and inefficient) of the efficient parent were utilized in analyses of plant traits. Statistically significant associations were identified between the zinc-efficient phenotype and mol Zn uptake mg-1 root, root-to-shoot ratio, specific root length, mol Zn uptake cm-2 root surface area, and Zn uptake cm-1 root length. No association was identified between zinc-efficient phenotype and root diameter, transpiration rate, or H+ production. Zinc uptake cm-1 root length had the greatest association with the zinc-efficiency phenotype and was able to discriminate the two phenotypic classes. We suggest that Zn uptake cm-1 root length is the most significant factor explaining the variation between the zinc-efficient and zinc-inefficient phenotypes in Exacum. 相似文献
18.
Y. P. S. Bajaj V. S. Rathore S. H. Wittwer M. W. Adams 《American journal of botany》1970,57(7):794-799
The effect of dimethyl sulfoxide (DMSO) on zinc65 uptake, respiration, RNA, and protein metabolism in various tissues of two bean (Phaseolus vulgaris L.) cultivars showing differential growth responses to zinc has been studied. At a concentration of 1%, DMSO stimulated zinc uptake in excised roots, stem-callus tissue, leaf disks, and enzymically isolated leaf cells, but did not significantly alter the uptake and incorporation of C14-uracil into RNA and C14-methionine into protein, although a slight inhibition was discernible in some tissues. At a higher concentration (10%) DMSO increased Zn65 uptake in excise roots incubated for 2 hr; however, at the same concentration, C14-uracil and C14-methionine uptake and incorporation were considerably inhibited in all the tissues. Oxygen uptake as measured with Warburg manometers was impaired, and the inhibition showed a time and concentration dependency. The fact that DMSO inhibited respiration and RNA and protein metabolism, while at the same concentration zinc uptake was increased, suggests that zinc uptake in beans is primarily a non-metabolic process. The possible mechanisms of DMSO action are discussed in the light of its reported effects on membrane permeability and cell metabolism. 相似文献
19.
Zinc is essential for normal development and function of the CNS although much is to be learned about brain Zn homeostasis. In these experiments adult male Wistar rats within the weight range 500–600 g were used. Ventriculo-cisternal perfusion was performed to allow the measurement of65Zn fluxes between blood and csf across the choroid plexuses. Blood-brain or blood-cerebrospinal fluid barrier permeability to65Zn has been determined by graphical analysis in experiments that lasted between 5 and 180 minutes. Cerebral capillary permeability to65Zn was found to be low with a Kin of about 5×10–4ml/min/g. Choroid plexus permeability to65Zn was about 12 fold greater, although Zn influx to brain via this route was <5% that across cerebral capillaries. The autoradiographic distribution of65Zn in brain showed regional variation with lowest levels in white matter and high levels in the dentate gyrus and hippocampus. 相似文献
20.
The mechanism(s) by which zinc is transported into cells has not been identified. Since zinc uptake is inhibited by reducing
the temperature, zinc uptake may depend on the movement of plasma membrane micoenvironments, such as endocytosis or potocytosis.
We investigated the potential role of potocytosis in cellular zinc uptake by incubating normal and acrodermatitis enteropathica
fibroblasts with nystatin, a sterol-binding drug previously shown to inhibit potocytosis. Zinc uptake was determined during
initial rates of uptake (10 min) following incubation of the fibroblasts in 50 μg nystatin/mL or 0.1% dimethyl-sulfoxide for
10 min at 37°C. The cells were then incubated with 1 to 30 μM
65zinc. Michaelis-Menten kinetics were observed for zinc uptake. Nystatin inhibited zinc uptake in both the normal and AE fibroblasts.
Reduced cellular uptake of zinc was associated with its internalization, not its external binding. In normal fibroblasts,
nystatin significantly reduced theK
m 56% and theV
max 69%. In the AE fibroblasts, nystatin treatment significantly reduced theV
max 59%, but did not significantly affect theK
m. The AE mutation alone affected theV
max for cellular zinc uptake. The control AE fibroblasts exhibited a 40% reduction inV
max compared to control normal fibroblasts. We conclude that nystatin exerts its effect on zinc uptake by reducing the velocity
at which zinc traverses the cell membrane, possibly through potocytosis. Furthermore, the AE mutation also effects zinc transport
by reducing zinc transport. 相似文献