1
|
Phiri FP, Ander EL, Lark RM, Joy EJM, Kalimbira AA, Suchdev PS, Gondwe J, Hamilton EM, Watts MJ, Broadley MR. Spatial analysis of urine zinc (Zn) concentration for women of reproductive age and school age children in Malawi. ENVIRONMENTAL GEOCHEMISTRY AND HEALTH 2021; 43:259-271. [PMID: 32862269 PMCID: PMC7847879 DOI: 10.1007/s10653-020-00700-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 08/18/2020] [Indexed: 05/04/2023]
Abstract
Zinc (Zn) is an essential micronutrient, and Zn deficiency remains a major global public health challenge. Recognised biomarkers of population Zn status include blood plasma or serum Zn concentration and proxy data such as dietary Zn intake and prevalence of stunting. Urine Zn concentration is rarely used to assess population Zn status. This study assessed the value of urine Zn concentration as a biomarker of population Zn status using a nationally representative sample of non-pregnant women of reproductive age (WRA) and school-aged children (SAC) in Malawi. Spot (casual) urine samples were collected from 741 WRA and 665 SAC. Urine Zn concentration was measured by inductively coupled plasma mass spectrometry with specific gravity adjustment for hydration status. Data were analysed using a linear mixed model with a spatially correlated random effect for between-cluster variation. The effect of time of sample collection (morning or afternoon), and gender (for SAC), on urine Zn concentration were examined. There was spatial dependence in urine Zn concentration between clusters among SAC but not WRA, which indicates that food system or environmental factors can influence urine Zn concentration. Mapping urine Zn concentration could potentially identify areas where the prevalence of Zn deficiency is greater and thus where further sampling or interventions might be targeted. There was no evidence for differences in urine Zn concentration between gender (P = 0.69) or time of sample collection (P = 0.85) in SAC. Urine Zn concentration was greater in afternoon samples for WRA (P = 0.003). Relationships between urine Zn concentration, serum Zn concentration, dietary Zn intake, and potential food systems covariates warrant further study.
Collapse
Affiliation(s)
- Felix P. Phiri
- School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire, LE12 5RD UK
- Department of Nutrition, HIV and AIDS, Ministry of Health, P. Bag B401, Lilongwe, Malawi
| | - E. Louise Ander
- Inorganic Geochemistry, Centre for Environmental Geochemistry, British Geological Survey, Nottingham, NG12 5GG UK
| | - R. Murray Lark
- School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire, LE12 5RD UK
| | - Edward J. M. Joy
- Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT UK
| | - Alexander A. Kalimbira
- Department of Human Nutrition and Health, Faculty of Food and Human Sciences, Bunda Campus, Lilongwe University of Agriculture and Natural Resources, P.O. Box 219, Lilongwe, Malawi
| | - Parminder S. Suchdev
- Department of Pediatrics and Hubert Department of Global Health, Emory University, Atlanta, GA 30322 USA
| | - Jellita Gondwe
- Community Health Sciences Unit, Ministry of Health, Private Bag 65, Lilongwe, Malawi
| | - Elliott M. Hamilton
- Inorganic Geochemistry, Centre for Environmental Geochemistry, British Geological Survey, Nottingham, NG12 5GG UK
| | - Michael J. Watts
- Inorganic Geochemistry, Centre for Environmental Geochemistry, British Geological Survey, Nottingham, NG12 5GG UK
| | - Martin R. Broadley
- School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire, LE12 5RD UK
| |
Collapse
|
2
|
Thalacker-Mercer AE, Gheller ME. Benefits and Adverse Effects of Histidine Supplementation. J Nutr 2020; 150:2588S-2592S. [PMID: 33000165 DOI: 10.1093/jn/nxaa229] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 03/02/2020] [Accepted: 07/09/2020] [Indexed: 01/05/2023] Open
Abstract
Histidine is a nutritionally essential amino acid with many recognized benefits to human health, while circulating concentrations of histidine decline in pathologic conditions [e.g., chronic obstructive pulmonary disease (COPD) and chronic kidney disease (CKD)]. The purpose of this review is to examine the existing literature regarding the benefits of histidine intake, the adverse effects of excess histidine, and the upper tolerance level for histidine. Supplementation with doses of 4.0-4.5 g histidine/d and increased dietary histidine intake are associated with decreased BMI, adiposity, markers of glucose homeostasis (e.g., HOMA-IR, fasting blood glucose, 2-h postprandial blood glucose), proinflammatory cytokines, and oxidative stress. It is unclear from the limited number of studies in humans whether the improvements in glucoregulatory markers, inflammation, and oxidative stress are due to reduced BMI and adiposity, increased carnosine (a metabolic product of histidine with antioxidant effects), or both. Histidine intake also improves cognitive function (e.g., reduces appetite, anxiety, and stress responses and improves sleep) potentially through the metabolism of histidine to histamine; however, this relation is ambiguous in humans. At high intakes of histidine (>24 g/d), studies report adverse effects of histidine such as decreased serum zinc and cognitive impairment. There is limited research on the effects of histidine intake at doses between 4.5 and 24 g/d, and thus, a tolerable upper level has not been established. Determining tolerance to histidine supplementation has been limited by small sample sizes and, more important, a lack of a clear biomarker for histidine supplementation. The U-shaped curve of circulating zinc concentrations with histidine supplementation could be exploited as a relevant biomarker for supplemental histidine tolerance. Histidine is an important amino acid and may be necessary as a supplement in some populations; however, gaps in knowledge, which this review highlights, need to be addressed scientifically.
Collapse
Affiliation(s)
- Anna E Thalacker-Mercer
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, USA.,Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Mary E Gheller
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, USA.,Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| |
Collapse
|
3
|
King JC, Brown KH, Gibson RS, Krebs NF, Lowe NM, Siekmann JH, Raiten DJ. Biomarkers of Nutrition for Development (BOND)-Zinc Review. J Nutr 2015; 146:858S-885S. [PMID: 26962190 PMCID: PMC4807640 DOI: 10.3945/jn.115.220079] [Citation(s) in RCA: 287] [Impact Index Per Article: 31.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Revised: 07/29/2015] [Accepted: 12/29/2015] [Indexed: 12/17/2022] Open
Abstract
Zinc is required for multiple metabolic processes as a structural, regulatory, or catalytic ion. Cellular, tissue, and whole-body zinc homeostasis is tightly controlled to sustain metabolic functions over a wide range of zinc intakes, making it difficult to assess zinc insufficiency or excess. The BOND (Biomarkers of Nutrition for Development) Zinc Expert Panel recommends 3 measurements for estimating zinc status: dietary zinc intake, plasma zinc concentration (PZC), and height-for-age of growing infants and children. The amount of dietary zinc potentially available for absorption, which requires an estimate of dietary zinc and phytate, can be used to identify individuals and populations at risk of zinc deficiency. PZCs respond to severe dietary zinc restriction and to zinc supplementation; they also change with shifts in whole-body zinc balance and clinical signs of zinc deficiency. PZC cutoffs are available to identify individuals and populations at risk of zinc deficiency. However, there are limitations in using the PZC to assess zinc status. PZCs respond less to additional zinc provided in food than to a supplement administered between meals, there is considerable interindividual variability in PZCs with changes in dietary zinc, and PZCs are influenced by recent meal consumption, the time of day, inflammation, and certain drugs and hormones. Insufficient data are available on hair, urinary, nail, and blood cell zinc responses to changes in dietary zinc to recommend these biomarkers for assessing zinc status. Of the potential functional indicators of zinc, growth is the only one that is recommended. Because pharmacologic zinc doses are unlikely to enhance growth, a growth response to supplemental zinc is interpreted as indicating pre-existing zinc deficiency. Other functional indicators reviewed but not recommended for assessing zinc nutrition in clinical or field settings because of insufficient information are the activity or amounts of zinc-dependent enzymes and proteins and biomarkers of oxidative stress, inflammation, or DNA damage.
Collapse
Affiliation(s)
- Janet C King
- Children’s Hospital Oakland Research Institute, Oakland, CA
- University of California, Davis, Davis, CA
| | - Kenneth H Brown
- University of California, Davis, Davis, CA
- Bill & Melinda Gates Foundation, Seattle, WA
| | | | - Nancy F Krebs
- University of Colorado School of Medicine, Aurora, CO
| | - Nicola M Lowe
- University of Central Lancashire, Preston, United Kingdom; and
| | | | | |
Collapse
|
4
|
Feng RN, Niu YC, Sun XW, Li Q, Zhao C, Wang C, Guo FC, Sun CH, Li Y. Histidine supplementation improves insulin resistance through suppressed inflammation in obese women with the metabolic syndrome: a randomised controlled trial. Diabetologia 2013; 56:985-94. [PMID: 23361591 DOI: 10.1007/s00125-013-2839-7] [Citation(s) in RCA: 125] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Accepted: 01/07/2013] [Indexed: 12/22/2022]
Abstract
AIMS/HYPOTHESIS Increased inflammation and oxidative stress are associated with insulin resistance (IR) and metabolic disorders. Serum histidine levels are lower and are negatively associated with inflammation and oxidative stress in obese women. The objective of this study was to evaluate the efficacy of histidine supplementation on IR, inflammation, oxidative stress and metabolic disorders in obese women with the metabolic syndrome (MetS). METHODS A total of 100 obese women aged 33-51 years with BMI ≥ 28 kg/m² and diagnosed with MetS were included following a health examination in the community hospital in this randomised, double-blinded, placebo-controlled trial. Participants were allocated to interventions by an investigator using sequentially numbered sealed envelopes and received 4 g/day histidine (n = 50) or identical placebo (n = 50) for 12 weeks. Participants then attended the same clinic every 2 weeks for scheduled interviews and to count tablets returned. Serum histidine, HOMA-IR, BMI, waist circumference, fat mass, serum NEFA, and variables connected to inflammation and oxidative stress were measured at baseline and 12 weeks. Participants, examining physicians and investigators assessing the outcomes were blinded to group assignment. In addition, the inflammatory mechanisms of histidine were also explored in adipocytes. RESULTS At 12 weeks, a total of 92 participants completed this trail. Compared with the placebo group (n = 47), histidine supplementation significantly decreased HOMA-IR (-1.09 [95% CI -1.49, -0.68]), BMI (-0.86 kg/m² [95% CI -1.55, -0.17]), waist circumference (-2.86 cm [95% CI -3.86, -1.86]), fat mass (-2.71 kg [95% CI -3.69, -1.73]), serum NEFA (-173.26 μmol/l [95% CI -208.57, -137.94]), serum inflammatory cytokines (TNF-α, -3.96 pg/ml [95% CI -5.29, -2.62]; IL-6, -2.15 pg/ml [95% CI -2.52, -1.78]), oxidative stress (superoxide dismutase, 17.84 U/ml [95% CI 15.03, 20.65]; glutathione peroxidase, 13.71 nmol/ml [95% CI 9.65, 17.78]) and increased serum histidine and adiponectin by 18.23 μmol/l [95% CI 11.74, 24.71] and 2.02 ng/ml [95% CI 0.60, 3.44] in histidine supplementation group (n = 45), respectively. There were significant correlations between changes in serum histidine and changes of IR and its risk factors. No side effects were observed during the intervention. In vitro study indicated that histidine suppresses IL6 and TNF mRNA expression and nuclear factor kappa-B (NF-κB) protein production in palmitic acid-induced adipocytes in a dose-dependent manner, and these changes were diminished by an inhibitor of NF-κB. CONCLUSIONS/INTERPRETATION Histidine supplementation could improve IR, reduce BMI, fat mass and NEFA and suppress inflammation and oxidative stress in obese women with MetS; histidine could improve IR through suppressed pro-inflammatory cytokine expression, possibly by the NF-κB pathway, in adipocytes.
Collapse
Affiliation(s)
- R N Feng
- Department of Nutrition and Food Hygiene, School of Public Health, Harbin Medical University, 157 Baojian Road, Harbin, Heilongjiang, People's Republic of China
| | | | | | | | | | | | | | | | | |
Collapse
|
5
|
Burjonrappa SC, Miller M. Role of trace elements in parenteral nutrition support of the surgical neonate. J Pediatr Surg 2012; 47:760-71. [PMID: 22498394 DOI: 10.1016/j.jpedsurg.2012.01.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Revised: 01/11/2012] [Accepted: 01/11/2012] [Indexed: 10/28/2022]
Abstract
BACKGROUND Parenteral nutrition (PN) has transformed the outcome for neonates with surgical problems in the intensive care unit. Trace element supplementation in PN is a standard practice in many neonatal intensive care units. However, many of these elements are contaminants in PN solutions, and contamination levels may, in themselves, be sufficient for normal metabolic needs. Additional supplementation may actually lead to toxicity in neonates whose requirements are small. METHODS An electronic search of the MEDLINE, Cochrane Collaboration, and SCOPUS English language medical databases was performed for the key words "trace elements," "micro-nutrients," and "parenteral nutrition additives." Studies were categorized based on levels of evidence offered, with randomized controlled trials and meta-analyses accorded the greatest importance at the apex of the data pool and case reports and animal experiments the least importance. Articles were reviewed with the primary goal of developing uniform recommendations for trace element supplementation in the surgical neonate. The secondary goals were to review the physiologic role, metabolic demands, requirements, losses, deficiency syndromes, and toxicity symptoms associated with zinc, copper, chromium, selenium, manganese, and molybdenum supplementation in PN. RESULTS Zinc supplementation must begin at initiation of PN. All other trace elements can be added to PN 2 to 4 weeks after initiation. Copper and manganese need to be withheld if the neonate develops PN-associated liver disease. The status of chromium supplementation is currently being actively debated, with contaminant levels in PN being sufficient in most cases to meet neonatal requirements. Selenium is an important component of antioxidant enzymes with a role in the pathogenesis of neonatal surgical conditions such as necrotizing enterocolitis and bronchopulmonary dysplasia. Premature infants are often selenium deficient, and early supplementation has shown a reduction in sepsis events in this age group. CONCLUSION Appropriate supplementation of trace elements in surgical infants is important, and levels should be monitored. In certain settings, it may be more appropriate to individualize trace element supplementation based on the predetermined physiologic need rather than using bundled packages of trace elements as is the current norm. Balance studies of trace element requirements should be performed to better establish clinical recommendations for optimal trace element dosing in the neonatal surgical population.
Collapse
Affiliation(s)
- Sathyaprasad C Burjonrappa
- Department of Nutrition and Pediatrics, Maimonides Infants and Children's Hospital, Brooklyn, NY 11219, USA.
| | | |
Collapse
|
6
|
Abstract
The prevalence of short bowel syndrome appears to be increasing because of more aggressive surgical and medical approaches to the management of neonatal intraabdominal catastrophies. Hence, a large cohort of neonates with intestinal failure occupies neonatal intensive care units, requiring chronic total parenteral nutrition (TPN) in hopes that the residual bowel will adapt, thereby permitting weaning of TPN. Alternatively, when there is no hope for adaptation, these infants are maintained on TPN in hopes that they will grow to a size and state of general health satisfactory for either isolated intestinal transplant when liver function is preserved or combined liver-intestinal transplantation when the liver is irreparably damaged. Thus, it is imperative to provide enough parenteral nutrition to facilitate growth while minimizing TPN constituents predisposing to liver damage. Liver disease associated with intestinal failure (IFALD) seems to occur due to a variety of host factors combined with deleterious components of TPN. Host factors include an immature bile secretory mechanism, bile stasis due to fasting, and repeated septic episodes resulting in endotoxemia. Many constituents of TPN are associated with liver damage. Excessive glucose may result in fatty liver and/or hepatic fibrosis, excessive protein may lead to reduced bile flow, and phytosterols present in intravenous lipid may produce direct oxidant damage to the liver or may impede cholesterol synthesis and subsequent bile acid synthesis. Parenteral strategies employed to minimize TPN damage include reducing glucose infusion rates, reducing parenteral protein load, and reducing parenteral lipid load. Furthermore, preliminary studies suggest that fish oil-based lipid solutions may have a salutary effect on IFALD. Ultimately, provision of enteral nutrition is imperative for preventing or reversing IFALD as well as facilitating bowel adaptation. While studies of trophic hormones are ongoing, the most reliable current method to facilitate adaptation is to provide enteral nutrition. Continuous enteral feeding remains the mainstay of enteral nutrition support.
Collapse
Affiliation(s)
- Jacqueline J Wessel
- Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229-3039, USA.
| | | |
Collapse
|
7
|
|
8
|
Bougle D. Effects of composition of diet on zinc metabolism and status. J Pediatr Gastroenterol Nutr 2000; 31:321-2. [PMID: 10997383 DOI: 10.1097/00005176-200009000-00025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
|
9
|
Wade A, Tucker HN. Antioxidant characteristics of L-histidine 11The work described in this manuscript was partially sponsored and funded by Cytos Pharmaceuticals, LLC. J Nutr Biochem 1998. [DOI: 10.1016/s0955-2863(98)00022-9] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
10
|
Abstract
OBJECTIVE To update some essential trace metals required in total parenteral nutrition. CONCLUSION Essential trace metals, chromium, copper, manganese, molybdenum, selenium, and zinc are added to parenteral fluids to prevent the development of deficiency syndromes. When possible, these metals should be monitored, even in patients on short-term total parenteral nutrition (TPN) to avoid deficiency or toxicity. Many of the nutrients or additives used in parenteral solutions may be contaminated with metals, such as aluminum or chromium. Such trace-metal monitoring becomes more critical in infants, and those on long-term TPN.
Collapse
Affiliation(s)
- F Y Leung
- Department of Laboratory Medicine, University Hospital, London, Ontario, Canada
| |
Collapse
|
11
|
Harraki B, Guiraud P, Rochat MH, Alary J, Favier A. Interactions related to trace elements in parenteral nutrition. PHARMACEUTICA ACTA HELVETIAE 1995; 70:269-78. [PMID: 8765694 DOI: 10.1016/0031-6865(95)00034-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Trace elements (TE) are now commonly added into the nutritive admixtures used in total parenteral nutrition (TPN) to prevent deficiencies which can be observed in patients undergoing long-term intravenous feeding. Although the needs in TE are not exactly known during a TPN, some of them must be considered as essential according to the results of studies dealing with general nutritional deficiencies. Among essential TE copper, iron and zinc are found at relatively high levels in organism. Chromium, manganese and selenium are also very important even though they are present at lower levels. In the case of a parenteral nutrition, the composition of the mixture is precisely defined and both digestion and absorption steps are shunted. Nevertheless, beneficial and/or negative physicochemical and metabolic interactions can occur between TE and the other nutrients. These interactions must be studied and taken into account because they can modify the bioavailability of the trace elements. In this article, our aim is to review the main recent bodies of knowledge which could be helpful to understand and prevent nutritional problems linked to these interactions during parenteral nutrition.
Collapse
Affiliation(s)
- B Harraki
- Laboratoire de Biochimie C, Hôpital A. Michallon, Grenoble, France
| | | | | | | | | |
Collapse
|
12
|
Heinen F, Matern D, Pringsheim W, Leititis JU, Brandis M. Zinc deficiency in an exclusively breast-fed preterm infant. Eur J Pediatr 1995; 154:71-5. [PMID: 7895760 DOI: 10.1007/bf01972977] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
UNLABELLED A formerly premature, exclusively breast-fed infant with severe zinc deficiency syndrome is presented. He showed the characteristic erosive skin changes, including alopecia, as seen in acrodermatitis enteropathica. In addition, he manifested a failure to thrive and irritability. The diagnosis was confirmed by reduced serum levels of zinc (2.3 mumol/l) and alkaline phosphatase (45 U/l). We consider the reduced zinc supply in the breast milk (5.7 mumol/l) as the most likely cause of the disease. Therapy consisted of oral zinc supplements (50 mumol/kg/day) for a period of 30 weeks. Symptoms and laboratory values normalized completely and did not recur on a normal diet. CONCLUSION A diet of breast milk can, in rare circumstances, cause insufficient zinc intake resulting in severe zinc deficiency syndrome with characteristic dermatological features. Therapy consists of temporary oral zinc supplementation at a daily dose of 50 mumol/kg.
Collapse
Affiliation(s)
- F Heinen
- Universitäts-Kinderklinik Freiburg, Germany
| | | | | | | | | |
Collapse
|
13
|
Faure H, Leverve X, Arnaud J, Boujet C, Favier A. Zinc changes in blood and urine during cyclic parenteral nutrition: relationships with amino acid metabolism. Br J Nutr 1994; 72:763-73. [PMID: 7826998 DOI: 10.1079/bjn19940078] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Serum Zn, ultrafiltrable Zn and amino acids in serum and urine samples of twenty-seven patients receiving cyclic (12 h/24 h) parenteral nutrition were measured. These samples were collected in patients after a 12 h period of parenteral nutrition, and in the evening after 12 h without parenteral nutrition. The same determinations were performed in ten control subjects who followed the same sampling scheme. Total serum ultrafiltrable Zn showed no significant variations in the patients during parenteral nutrition, and was not significantly different in the two groups although the proportion of the Zn present in the ultrafiltrable fraction was elevated. Serum cystine levels were significantly higher (P = 0.05) in the patients than the control subjects, and cystine excretion was also higher in patients (P < 0.05) and increased after parenteral nutrition (56.0 (SE 6.5) v. 147.1 (SE 20.6) mumol/12 h; P < 0.001). Histidine levels did not vary significantly in serum after parenteral nutrition and were not different in the patients in comparison with the control subjects. Histidine excretion was not different in the two groups but increased significantly during parenteral nutrition (P < 0.05). Serum albumin was significantly depressed in the patients compared with the control subjects (45.3 (SE 1.5) v. 33.9 (SE 1.5) g/l; P < 0.001). These results suggest that cystine infusion and excretion relate to the changes occurring in serum Zn and in urinary Zn excretion.
Collapse
Affiliation(s)
- H Faure
- Laboratory of Biochemistry C, University Hospital, Grenoble, France
| | | | | | | | | |
Collapse
|
14
|
Gachot B, Tauc M, Morat L, Poujeol P. Zinc uptake by proximal cells isolated from rabbit kidney: effects of cysteine and histidine. Pflugers Arch 1991; 419:583-7. [PMID: 1788054 DOI: 10.1007/bf00370299] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The aim of this study was to characterize the mechanisms of zinc transport in proximal cells isolated from rabbit kidney cortex. Uptakes of 65Zn were assessed under initial rate conditions, after 0.5 min of incubation. The kinetic parameters obtained at 20 degrees C were a Km of 15.0 +/- 1.5 microM, a Jmax of 208.0 +/- 8.4 pmol min-1 (mg protein)-1, and an unsaturable constant of 0.259 +/- 0.104 (n = 8). Cadmium competitively inhibited the zinc uptake, with a Ki value of 13.0 +/- 2.8 microM, while zinc competitively inhibited 109Cd uptake by isolated cells. Cysteine and histidine stimulated zinc transport at an amino acid:zinc molar ratio ranging from 1:1 to 8:1. This stimulation was not observed in the absence of a sodium gradient. At a molar ratio greater than 16:1 (i.e. 400 microM cysteine or histidine and 25 microM Zn), there was evidence of inhibition. These data suggest that zinc enters renal proximal cells (a) as a free ion via a saturable carrier-mediated process or an unsaturable pathway and (b) complexed with cysteine or histidine, by means of a sodium/amino acid cotransport mechanism.
Collapse
Affiliation(s)
- B Gachot
- Département de Biologie cellulaire et moléculaire, CEN Saclay, Gif sur Yvette, France
| | | | | | | |
Collapse
|