![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
![[Contents]](/icons/banner/tocACT.gif){kind=icon}
|
|
|
|
|
||
May Explain Diarrhea Associated with Zinc Deficiency1
Department of Pediatric Surgery and * First Department of Surgery, Osaka University Medical School, Osaka 565, Japan
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
ACKNOWLEDGMENTS
FOOTNOTES
LITERATURE CITED
ABSTRACT 
Synthesis of inducible nitric oxide synthase (iNOS) in the intestine may result in local tissue damage. We investigated whether a challenge with interleukin-1
could give rise to intestinal iNOS expression and diarrhea in rats of differing zinc status. Weaning male rats were fed a zinc-deficient (ZD) diet (2 mg zinc/kg) for 4 wk to induce zinc deficiency or a zinc-supplemented diet [50.8 mg zinc/kg; controls, including pair-fed (PF ) and ad libitum (AL) consumption groups], and then subcutaneously injected with interleukin-1 (2 × 107 units/kg body wt). Without the interleukin-1 challenge, ZD rats had significantly lower plasma zinc concentration than the other groups. Intestinal metallothionein-1 mRNA abundance was lower in ZD rats than in AL rats. iNOS was expressed in the intestine of ZD rats but not in the others. None of the rats experienced diarrhea during the feeding period. Interleukin-1 led to a reduction in plasma zinc concentration, enhancement in intestinal metallothionein-1 mRNA levels, and expression of the intestinal iNOS gene in all groups. However, the abundance of iNOS mRNA was significantly higher in ZD rats than in the other groups. The presence of iNOS protein was demonstrated by immunohistochemical staining in the intestine of ZD rats that had been treated with interleukin-1 12 h earlier. In addition, diarrhea occurred in most of the ZD rats and some of the PF rats but not in AL rats after interleukin-1 treatment. We conclude that ZD rats respond to interleukin-1 challenge more severely than controls, reflected by a more marked and prolonged iNOS expression and a greater incidence of diarrhea.
·
nitric oxide synthase ·
metallothionein ·
zinc ·
rats ·
diarrhea
INTRODUCTION
Nitric oxide, a free radical gas, is an important regulatory factor in physiological processes (Vallance and Moncada 1994
). The intestine possesses both the calciumdependent constitutive nitric oxide synthase and the calcium-independent inducible nitric oxide synthase (iNOS)3; this has been demonstrated under lipopolysaccharide stimulation (Tepperman et al. 1993). Nitric oxide production by the constitutive enzyme plays many physiological roles, including the regulation of gastrointestinal blood flow and mucosal integrity (Hutcheson et al. 1990); however, a large amount of nitric oxide produced by iNOS, which can be induced by endotoxin and certain cytokines, is associated with a decrease in cellular viability and may result in local intestinal damage (Tepperman et al. 1993). Moreover, an excessive production of nitric oxide may play a pivotal role in castor oil-induced diarrhea, diphenylmethane-related diarrhea (Gaginella et al. 1994), and diarrhea in morphine withdrawal syndrome (Vaupel et al. 1995). On the other hand, diarrhea has been recognized as one of the gastrointestinal symptoms of zinc deficiency in humans for 20 y (Okada et al. 1976). However, the underlying mechanism of zinc deficiency-associated diarrhea is not fully understood.
|
Table 1. Composition of the diet1 |
Interleukin-1 (IL-1) is one of the cytokines and acts in part to induce the acute-phase response. It is involved in a complex cascade of biological events, including hormone production and changes in the distribution of minerals between storage and transport pools. Administration of IL-1 results in redistribution of zinc and regulates metallothionein mRNA expression in tissues of rats (Cousins and Leinart 1988), whereas the latter can be altered by dietary levels of zinc (Blalock et al. 1988). IL-1 has also been reported to induce iNOS gene expression or nitric oxide production in many tissues and cells (Willis et al. 1994). In addition, changes in systemic and local levels of IL-1 are associated with diarrhea occurrence (Rinehart et al. 1994). Whether iNOS could be expressed in the intestine and relate to zinc deficiency-associated diarrhea has not been established.
Accordingly, in this study, we examined whether an IL-1 challenge could induce iNOS expression in the intestine of rats of different zinc status. Plasma zinc concentration and intestinal metallothionein mRNA were examined to reflect dynamic change in zinc metabolism. Simultaneously, the incidence of diarrhea was monitored before and after IL-1 administration.
MATERIALS AND METHODS
was kindly donated by DaiNippon Pharmaceutical, Osaka, Japan (Lot No: HL-18). Specific activity was 2.01 × 107 units/mg protein in a concentration of 4.96 g protein/L (by micro-Kjeldahl method).
Experimental protocol.
Diarrhea was recognized as unformed, watery feces and was monitored and recorded daily during the feeding period. After 4 wk of consuming the diets, rats were injected subcutaneously with IL-1 (2 × 107 units/kg body wt) or PBS according to the group subdivision, and were placed into the metabolism cages. There were 70 rats in each group; one-half were administered IL-1 and the other half, PBS. Therefore each time point for IL-1 or PBS administration included five rats. The care of the metabolism cages was the same as before the injection except that the feces separator installed at the bottom of the cages was thoroughly cleaned. The individual cages and rats were inspected at the indicated time points for the presence of characteristic diarrheal droppings on the separator and tarry diarrhea, defined by perianal spotting. The appearance of one or both of the manifestations was recorded as a positive observation. Rats were killed at 0, 3, 6, 12, 24, 48 and 72 h after administration of the injection. Heparinized blood was collected from abdominal aorta of rats under ethyl ether anesthesia. Plasma was separated and stored at 
20°C until use. Intestinal samples for RNA analysis were taken from the upper jejunum and processed immediately.
|
Table 2.
Incidence of diarrhea after interleukin-1 |
(IL-1) administration. Two hundred ten male weaning rats were divided intothe following three groups: ad libitum (AL) and pair-fed (PF ) groups fed a semipurified zinc-supplemented diet (50.8 mg zinc/kg diet) and a zinc-deficient (ZD) group fed a zinc-deficient diet (2 mg zinc/kg diet). After 4 wk of consuming the diets,rats were injected subcutaneously with IL-1 (2 × 107 units/kg body wt) or PBS. They were killed by exsanguination at 0, 3, 6, 12, 24, 48 and 72 h after administration of IL-1 or PBS for determination of plasma zinc level. Values are means ± SD, n = 5 at each time point. *P < 0.05, significantly different than basal level (0 h) or PBS-treated group at the same time, by two-way ANOVA and Fisher's protected least significant difference test.
(IL-1) or PBS. Northern blot experiments were performed using 20 µg of total RNA in each lane. Probes used were 186-bp MT-1 cDNA and 1.1-kb GAPDH cDNA. Both probes were randomly labeled with [-32P]dCTP. The results shown are representative of three separateexperiments. (A) Administration with PBS. To correct for loading differences, the densitometric signal for each RNA sample hybridized to the MT-1 probe was divided by that hybridized to the GAPDH probe. Lower panel: corrected values are plotted as a percentage of that for AL. *P < 0.05 vs. AL according to one-way ANOVA and Scheffé's F-test. (B) Administration with IL-1 (2 × 107 units/kg body wt).
(IL-1, 2 × 107 units/kg body wt). cDNA were synthesized from total RNA samples (1 µg for each) with random 9-mer primers and Avian Myeloblastosis Virus reverse transcriptase. The cDNAs were then amplified by PCR with synthetic gene-specific primers for iNOS or GAPDH for 30 cycles before the plateau phases. Top: RT-PCR products electrophoresed on 2% agarose gels containing ethidium bromide. A 430 bp single band for iNOS and a 702 bp for GAPDH in each lane were visualized by UV fluorescence. Bottom: ratio of iNOS mRNA/GAPDH mRNA from relative intensities analyzed by NIH Image 1.55 software. Values are means ± SD derived from three experiments. Significant differences (by two-way ANOVA and Scheffé's F-test) are *P < 0.05 vs. respective AL or PF at the same time; 
P < 0.05 vs. basal level (0 h).
(IL-1). Diffuse yellow-brown staining observed throughout the cytoplasm indicates binding of the iNOS-antibody complex. (C ) and (D ) Intestinal tissue sections (7 µm) processed for iNOS immunohistochemistry. Samples were taken from ad libitum (AL) and zinc-deficient (ZD) rats that were fed a 50.8 (control) or 2 (deficiency ) mg zinc/kg diet for 4 wk and then injected with IL-1 (2 × 107 units/kg body wt) or PBS. (C) Intestinal section from an AL rat injected with PBS 12 h before; note that iNOS immunoreactivity is not present. (D) Section from a ZD rat injected with IL-1 12 h earlier. iNOS immunoreactivity, diffused yellow-brown staining, is present mainly in the basal layer and scattered in villus cells. Arrows indicate the positive staining. In (A ) and (B ), the bar is equivalent to 25 µm; in (C ) and (D ), the bar is equivalent to 100 µm.
Determination of zinc concentration. Plasma was digested by 1 mol/L hydrochloric acid as described previously (Takagi et al. 1986
). The zinc concentrations were measured by atomic absorption spectrophotometry (Z-6100 simultaneous multielement atomic absorption spectrophotometer, Hitachi Instrument, Tokyo, Japan).
RNA isolation and Northern blot analysis.
Total RNA was extracted from tissues with the use of a commercial reagent ISOGEN (Nippon Gene, Tokyo, Japan). Briefly, 6 cm of small intestine was excised, pancreatic attachments and fat were removed and the lumen was flushed with ice-cold saline. The samples were homogenized directly in ISOGEN solution (~200 g/L). The homogenate was mixed with 0.2 volumes of chloroform. After centrifugation at 12,000 × g for 15 min at 4°C, the supernatant was transferred to a new tube and mixed with an equal volume of isopropanol to precipitate RNA. After centrifugation as above, the pellet was washed with 75% ethanol, recentrifuged at 10,000 × g for 5 min at 4°C, air dried and then dissolved in diethyl pyrocarbonate-treated distilled water. The concentration of RNA was estimated from the absorbance at 260 nm (the ratio at 260/280 was between 1.6 and 1.9). Total RNA (20 µg) was electrophoresed through 10 g/L agarose/formaldehyde gels in 3-(N-morphlino) propanesulfonic acid buffer, pH 7.0, transferred to nylon membranes (Hybond N+, Amersham, Buckinghamshire, England) with 20 × standard saline citrate as blotting buffer, and cross-linked to membrane by UV irradiation followed by baking at 80°C for 2 h. Methylene blue staining was used to verify ribosomal subunit integrity. Blots were prehybridized with QuikHyb Hybridization Solution (Stratagene, La Jolla, CA) at 60°C for 30 min. Hybridization was conducted in fresh hybridization solution containing metallothionein-1 cDNA probe from reverse transcription polymerase chain reaction (RT-PCR), as described in the next section, at 60°C for 1 h. Membranes were washed twice in 2 × standard saline citrate containing 1 g/L SDS for 20 min and then in 0.1 × standard saline citrate containing 1 g/L SDS at 60°C for 30 min. After exposure, the membranes were subsequently stripped and rehybridized with a human glyceraldehyde-3-phosphate-dehydrogenase (GAPDH) cDNA probe (1.1 kb) (Clontech Laboratories, Palo Alto, CA) to control for loading errors or transfer variations. The cDNA probes used for metallothionein-1 and GAPDH were labeled with [-32P]dCTP (111 TBq/mmol) by the random-primed labeling method.
Reverse transcription polymerase chain reaction.
Analysis of mRNA levels for iNOS by RT-PCR was performed by a standard method. Briefly, the first strand DNA was synthesized using random 9-mer primers and Avian Myeloblastosis Virus reverse transcriptase (Takara Shuzo, Shiga, Japan) followed by PCR amplification using synthetic gene specific primers for rat iNOS (forward 20-mer, 5
-GCT ACA CTT CCA ACG CAA CA-3; reverse 20-mer, 5-TGG GTG GGA GGG GTA GTG AT-3), which should produce a 430-bp product for iNOS mRNA. PCR amplifications were performed according to the following schedule: denaturation, annealing and elongation at 94, 60 and 72°C for 1 min, 1 min 30 s and 1 min 30 s, respectively, for 30 cycles. To ensure that equal amounts of reverse-transcribed RNA were added to the PCR reaction, the parallel amplification of GAPDH mRNA was performed as an internal reference, using forward 20-mer, 5-GCC ATC AAC GAC CCC TTC AT-3, and reverse 20-mer, 5-CGC CTG CTT CAC CAC CTT CT-3, which should give a 702-bp product. The plateau phases of PCR for iNOS and GAPDH occurred at more than 40 and 35 cycles, respectively. Therefore the PCR products were obtained before the plateau cycles. PCR products were electrophoresed on 20 g/L agarose gels containing ethidium bromide and visualized by UV-induced fluorescence. A HaeIII digest of 
174 DNA (GIBCO-BRL Life Technologies, Gaithersburg, MD) was used as a size marker. The relative intensity was analyzed by NIH Image 1.55 software. Metallothionein-1 cDNA was obtained by RT-PCR described as above with synthetic gene specific primers for rat metallothionein-1 (forward 20-mer, 5-CCC AAC TGC TCC TGC TCC AC-3; reverse 20-mer, 5-GTC ACT TCA GGC ACA GCA CG-3). The 186-bp cDNA for metallothionein-1 mRNA was used in the Northern blot hybridization.
Immunohistochemistry.
Immunohistochemical staining of iNOS was performed with DAKO LSAB Kit HRP (DAKO, Carpinteria, CA). Fresh, unfixed tissue frozen in OCT (Miles, Elkhart, IN) was sectioned with a cryostat. Adjacent sections were placed on duplicate slides. Sections were air-dried at room temperature for 30 min, fixed with acetone at 4°C for 10 min and rehydrated in PBS for 15 min. They were then treated with 3% H2O2 for 30 min and washed with wash buffer (PBS containing 0.1% Triton X-100) for 15 min. Sections were blocked for 15 min with 10 g/L bovine serum albumin and for 15 min with 10% normal goat serum and then incubated with 1:100 anti-iNOS rabbit polyclonal IgG (Upstate Biotechnology, Lake Placid, NY) for 1 h at room temperature. Control sections were incubated with control rabbit IgG. After being washed with wash buffer for 15 min, sections were incubated in biotinylated goat anti-rabbit IgG at room temperature for 30 min. The sections were washed with wash buffer. Streptavidin-peroxidase conjugate was applied for 15 min. Sections were washed again with wash buffer, and the specific iNOS spots were visualized by diaminobenzidine (DAB) chromagen. After nuclear staining, the sections were washed again, dried and mounted. Cultured vascular smooth muscle cells from rat thoracic aorta, which have been demonstrated to produce large amounts of nitric oxide by stimulation with IL-1 (Scott-Burden et al. 1994), were used as a positive control to test the ability of the anti-iNOS IgG in detecting iNOS expression.
Statistical analysis.
Data were expressed as means ± SD. Differences between groups in basal plasma zinc concentration and metallothionein-1 mRNA level were determined using one-way ANOVA; changes in plasma zinc concentration and iNOS/GAPDH mRNA ratio after IL-1 or PBS administration were analyzed by two-way ANOVA, followed by Scheffé's F-test or Fisher's protected least significant difference test as indicated in the figure legends. The statistics of the incidence of diarrhea was by chi-square test. The statistical software Statview-J 4.1 (Abacus Concepts, Berkeley, CA) was used on an Apple Macintosh computer. A value of P < 0.05 was considered to be significant.
RESULTS
administration. Diarrhea was observed in most ZD rats and some PF rats 6 h after administration of IL-1, whereas it did not appear in AL rats following IL-1 administration. The incidence of diarrhea was significantly higher in ZD rats than in both other groups (Table 2).
treatment, plasma zinc concentration in ZD rats was significantly lower than those in PF and AL rats (2.0 ± 0.4, 13.6 ± 2.1 and 20.9 ± 1.5 µmol/L, respectively; P < 0.001 between ZD and PF or AL rats, P < 0.001 between PF and AL rats, by one-way ANOVA and Scheffé's F-test).
administration, plasma zinc concentrations in all groups were gradually reduced to 50, 75 and 82% of the time-zero levels by 6 h in ZD, PF and AL rats, respectively, and returned to the time-zero levels by 48 h (Fig. 1).
administration, expression of metallothionein-1 mRNA in the intestine of ZD rats was significantly lower than that in AL rats (Fig. 2A). IL-1 challenge elevated metallothionein-1 mRNA levels in all three groups with a maximum at 3 or 6 h (Fig. 2B).
challenge. Administration of IL-1 induced iNOS gene expression in all of rats with the maximal abundance at 6 h. The expression was significantly higher in ZD rats compared with AL or PF rats during the 72-h observation period (Fig. 3). The ratio of iNOS mRNA/GAPDH mRNA from relative intensities in PF rats was similar to that in AL rats at each time point following IL-1 administration.
administration, no iNOS immunoreactivity was detectable on intestinal sections at 12 h (results not shown). However, in ZD rats 12 h after administration of IL-1, iNOS immunoreactivity was observed in the intestinal sections. The appearance of iNOS staining was compared with a negative control section from an AL rat without IL-1 administration, and a pair of positive and negative control stainings in vascular smooth muscle cells. The positive staining in ZD rat intestine was present mainly in the basal layer and scattered in villus cells (Fig. 4).
DISCUSSION
administration can induce iNOS gene expression in small intestine of rats of differing zinc status and induce diarrhea in zinc-deficient and malnourished (PF ) rats. Furthermore, ZD rats had a more severe response to IL-1 than controls, reflected by a more marked and prolonged iNOS gene expression and a higher incidence of diarrhea.
iNOS, interleukin-1, diarrhea and zinc deficiency.
The observation that iNOS mRNA was undetectable before IL-1 challenge in the intestine of AL rats was anticipated because iNOS usually cannot be expressed in healthy tissues (Tepperman et al. 1993). Although malnutrition shown by relative low plasma zinc concentration and growth retardation was also observed in PF rats, RT-PCR analysis failed to detect intestinal expression of iNOS mRNA in PF rats before IL-1 administration. It is not surprising, however, that expression of iNOS gene in small intestine was already observed in ZD rats before IL-1 challenge. We previously reported that prolonged zinc deficiency induces morphological alteration of intestines, such as thinner muscular layer, smaller and more pointed villi and flawed brush border (Cui et al. 1996). The iNOS mRNA in the intestine of ZD rats observed before IL-1 challenge may be related to the structural change. In addition, dermatitis occurred in all of the ZD rats during the 4-wk feeding period; ZD rats may therefore have had chronically elevated levels of systemic proinflammatory cytokines. The iNOS protein, however, likely was very low because the immunoreactivity was not detected before IL-1 administration.
). The incidence of persistent diarrhea and dysentery has also reportedly been reduced by zinc supplementation (Sazawal et al. 1996). On the other hand, diarrhea is not a usual finding in experimentally induced zinc-deficient rats, although it is one of manifestations in other animals with severe zinc deficiency. Several lines of evidence suggest that zinc deficiency-associated diarrhea is related to morphological changes in the intestine and impairments of immune function including lymphoid tissue atrophy, reduction in lymphocyte count and T-helper cell proportion, cytotoxic activity of lymphocytes and natural killer cell activity. However, the underlying mechanism has not been fully clarified.
). Lipopolysaccharide promotes a dramatic increase of intestinal mucus secretion in mice; the kinetics of secretion correlates with intestinal IL-1 levels, and this response is attenuated by specific blockage with the IL-1 receptor antagonist protein (Mester et al. 1993). Various investigators have documented that IL-1 is a potent mucus secretagogue of mouse intestinal explants in vitro (Cohan et al. 1991) and increases short-circuit current of rabbit (Chiossone et al. 1990) and chicken (Chang et al. 1990) mucosal explants in Ussing chambers. IL-1 reduces Na+ and Cl
absorption by rabbit ileal mucosa by a mechanism independent of extracellular Ca2+ and possibly in part in relation to arachidonic acid metabolism (Chiossone et al. 1990). The mechanism of the effect, however, on secretory activity of bowel mucosa by IL-1 is not fully understood.
). Therefore, iNOS expression leads to the production of large amounts of nitric oxide (Iadecola et al. 1995). High levels of nitric oxide are cytotoxic (Beckman et al. 1990). It is also possible that an accumulation of fluid in the intestinal lumen in response to exposure to bacterial toxins may be a result of disruption of the regulatory mechanisms of villus cell function as well as the stimulation of secretory activity by crypt cells following excessive nitric oxide production by the inducible enzyme (Tepperman et al. 1993). Furthermore, excess nitric oxide produced by iNOS may result in disorder of movement in intestinal muscles, such as relaxation of intestinal circular muscle, promoting a greater ease of flow (transit) from proximal to distal intestinal segments. Inflammatory conditions affecting the bowel are usually linked to disturbances in intestinal motility (Mathias and Clench 1989), which is related to overproduction of nitric oxide produced by iNOS (Mourelle et al. 1996). Both the transcription and translation data documented that iNOS was present in the small intestine of ZD rats after IL-1 administration.
administration.
Dietary zinc deficiency induced a marked reduction of plasma zinc level that was ~10% of the levels of AL rats without IL-1 treatment. IL-1 administration further induced a reduction of plasma zinc concentration by 50% compared with the level at time zero in ZD rats. It has been reported that the acute-phase response to injury or infection, involved in systemic physiological and biochemical alterations, is associated with activation of neuroendocrine and cytokine pathways and a fall in plasma zinc concentration (Shenkin 1995). The results in our study are consistent with the previous reports, suggesting that the inflammatory response may further aggravate zinc deficiency through zinc redistribution.
Metallothionein mRNA expression and IL-1 administration.
Metallothioneins are cystine-rich, low molecular weight proteins with high affinity for physiological and nonphysiological heavy metals (Mengheri et al. 1993). Although their biologic roles are still the subject of debate, they undoubtedly act as a store for metals such as zinc. Their concentrations in tissues are highly dependent on metal-ion availability; much of the regulation occurs at the level of transcription (Chesters 1992). Metallothionein mRNA expression is closely regulated by the dietary supply of zinc, and the levels in some tissues are a direct reflection of zinc intake (Blalock et al. 1988, Huber and Cousins 1988). Experimental evidence based on metallothionein null, metallothionein transgenic (overexpression of metallothionein-1) and normal mice further shows that metallothionein plays an important role in the maintenance of zinc homeostasis (Davis et al. 1996). Our results from Northern blot analysis showed good agreement with previous reports (Blalock et al. 1988, Huber and Cousins 1988) and reconfirmed that dietary zinc supply affects metallothionein mRNA expression in rat intestine. Interestingly, ZD rats showed the same enhanced metallothionein mRNA expression as a result of IL-1 stimulation as did PF and AL rats, indicating that metallothionein mRNA synthesis induced by IL-1 was independent of zinc level of tissue because IL-1 injection deprives the intestine of zinc (Cousins and Leinart, 1988).
challenge; 2 ) the levels of iNOS mRNA induced by IL-1 were much higher in ZD than in PF and AL rats; and 3 ) after administration of IL-1, iNOS protein was clearly visualized in basal layer and villus cells in the intestine of ZD rats.
ACKNOWLEDGMENTS
FOOTNOTES
Manuscript received 8 October 1996. Initial reviews completed 27 November 1996. Revision accepted 28 April 1997.
LITERATURE CITED
This article has been cited by other articles:
|
|
 |
|
  B. J. Niles, M. S. Clegg, L. A. Hanna, S. S. Chou, T. Y. Momma, H. Hong, and C. L. Keen Zinc Deficiency-induced Iron Accumulation, a Consequence of Alterations in Iron Regulatory Protein-binding Activity, Iron Transporters, and Iron Storage Proteins J. Biol. Chem., February 22, 2008; 283(8): 5168 - 5177. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 W. Altaf, S. Perveen, K. U. Rehman, S. Teichberg, I. Vancurova, R. G. Harper, and R. A. Wapnir Zinc Supplementation in Oral Rehydration Solutions: Experimental Assessment and Mechanisms of Action J. Am. Coll. Nutr., February 1, 2002; 21(1): 26 - 32. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. Cui, R. K. Blanchard, L. M. Coy, and R. J. Cousins Prouroguanylin Overproduction and Localization in the Intestine of Zinc-Deficient Rats J. Nutr., November 1, 2000; 130(11): 2726 - 2732. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. A. Wapnir Zinc Deficiency, Malnutrition and the Gastrointestinal Tract J. Nutr., May 1, 2000; 130(5): 1388S - 1392. [Abstract] [Full Text]
|
|
|
|
|
|
R. K. Blanchard and R. J. Cousins Regulation of Intestinal Gene Expression by Dietary Zinc: Induction of Uroguanylin mRNA by Zinc Deficiency J. Nutr., May 1, 2000; 130(5): 1393S - 1398. [Abstract] [Full Text]
|
|
|
|
|
|
L. Cui, Y. Takagi, M. Wasa, K. Sando, J. Khan, and A. Okada Nitric Oxide Synthase Inhibitor Attenuates Intestinal Damage Induced by Zinc Deficiency in Rats J. Nutr., April 1, 1999; 129(4): 792 - 798. [Abstract] [Full Text]
|
|
|
|
|
|
L. Cui, Y. Takagi, M. Wasa, Y. Iiboshi, M. Inoue, J. Khan, K. Sando, R. Nezu, and A. Okada Zinc Deficiency Enhances Interleukin-1alpha -Induced Metallothionein-1 Expression in Rats J. Nutr., July 1, 1998; 128(7): 1092 - 1098. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
