Factors underlying abnormal zinc metabolism in uremia

Zinc balance studies were completed in ten hemodialyzed adult uremic patients and five normal controls to determine the cause of abnormal zinc metabolism in uremia. Subjects were fed standard hospital foods providing nutrients in amounts recommended for adult stable hemodialyzed patients. The amount of zinc in the diet was kept constant at 10 mg per day. After one week of stabilization, blood, urine, used dialysate (in patients on dialysis days) and stool samples were collected daily for the next two weeks. In comparison to controls, patients had lower plasma zinc levels (mean +/- SD, 112 +/- 10 vs. 82 +/- 12 micrograms/dl, P less than 0.01), lower urinary zinc excretion (560 +/- 120 vs. 40 +/- 20 mg/24 hrs, P less than 0.001) and higher fecal zinc losses (8.1 +/- 0.7 vs. 10.2 +/- 0.6 mg/24 hrs, P less than 0.01). Dialytic zinc losses were minimal (26 +/- 4 micrograms/treatment). During the study period, patients were in a negative zinc balance while normal controls maintained a positive zinc balance on 10 mg dietary zinc intake. These results demonstrate that augmented fecal zinc excretion in the presence of hypozincemia contributes to the negative zinc balance in hemodialyzed uremic patients.

Intrinsic and extrinsic stable isotopic zinc absorption by infants from formulas

The kinetics of fecal elimination and the extent of fractional absorption of intrinsic and extrinsic zinc from infant formula were studied in 11 human infants by using a direct, simultaneous dual-label method based on fecal monitoring of unabsorbed stable isotope labels. The relative positions of the two stable isotopic tags (67Zn, 70Zn) as extrinsic and intrinsic labels were reversed in two separate determinations of fractional absorption. Administration of doubly labeled formula for 24 h or less permitted elimination of unabsorbed labels before the end of a 72-h metabolic interval. The extent of enrichment and the kinetics of fecal elimination of unabsorbed extrinsic stable isotopic zinc tag were observed to agree closely with the corresponding values for the intrinsic tag. Fractional absorption of intrinsic and extrinsic tags was highly correlated and did not differ significantly. The ratio of fractional absorption of extrinsic tag to that of intrinsic tag was 1.05 +/- 0.19 (mean +/- SD). The results constitute strong support for validation of the use of enriched stable isotopes at low levels (less than or equal to 10%) of extrinsic addition to milk-based diets for studies of zinc absorption by humans.

Cadmium in blood, urine and hair related to human hypertension

A case-control study was performed to assess whether cadmium is related to hypertension in a non-occupationally exposed population. 63 male subjects affected by mild stable hypertension, pharmacologically untreated, were investigated together with 63 male normotensive controls individually matched for sex, age, body mass index, smoking habits and work activities. Cadmium in blood, zinc and copper in serum, the three elements in urine and hair, together with some biological parameters involved in pathogenesis of hypertension, were investigated. The mean Cd blood value in hypertensives (H) was 0.58 micrograms/L vs 0.44 micrograms/L in normotensives (N) (t = 2.03; p less than 0.05) with a greater difference in non-smokers (0.41 micrograms/L vs 0.25 micrograms/L) (t = 2.69, p less than 0.01). Furthermore, both systolic and diastolic blood pressure were significantly related to cadmium blood levels (r = 0.20 and 0.19 respectively, p less than 0.05). Smoking habit affected cadmium levels only in the blood, not in the other biological matrices examined. No significant difference of cadmium content in urine and hair was found between normotensives and hypertensives but Cd/Cu ratio in urine was significantly lowered in the second group.

Trace metal interactions in vivo: inorganic cobalt enhances urinary copper excretion without producing an associated zincuresis in rats

The effects of cobalt chloride on copper and zinc metabolism in male Sprague-Dawley rats were examined. These effects were compared with those of penicillamine, a chelating agent utilized in the therapy of the genetic abnormality of copper metabolism in humans, Wilson's disease. Cobalt elicited an increased (approximately 4-fold) urinary excretion of copper lasting through 72 h following a single cobalt dose. In contrast to the marked increase in urinary zinc excretion produced by penicillamine, cobalt greatly reduced (approximately 75%) zinc output in urine. Tissue copper and zinc concentrations were measured after treatment with cobalt at doses ranging from 12 to 60 mg/kg body weight. Substantially reduced (approximately 25%) renal copper concentration was observed at 1 and 3 d after cobalt administration. In addition, cobalt produced a concurrent dose-dependent elevation (up to 1.6-fold) in hepatic zinc concentration. Cytosolic zinc was eluted from a Sephadex G-75 column in the molecular weight region associated with metallothionein. Time-dependent induction of metallothionein concentration (10-fold) in liver by cobalt was confirmed by the cadmium/hemoglobin affinity assay. The ability of inorganic cobalt to elevate zinc concentration in liver and produce increased urinary copper excretion without the zincuresis that normally accompanies penicillamine administration represents a newly defined biological property of this essential trace metal.

Interaction of niacin and zinc metabolism in patients with alcoholic pellagra

The effect of zinc supplementation on the metabolism of tryptophan conversion to niacin was studied in 14 alcoholic patients with pellagra and in 7 male control subjects aged 21-45 y. The pellagrins received chemically defined diets based on crystalline amino acids through an enteral tube for 7 d. Patients were divided into two groups (A and B), both receiving a diet from which tryptophan, Zn, and niacin were excluded. Patients in group B, however, received 220 mg Zn sulfate orally. Upon admission the pellagra patients had low plasma Zn levels and low urinary excretion values of N'methylnicotinamide (N'MN) and N'methyl-2-pyridone-5-carboxamide (2-PYR) in relation to the control subjects (p less than 0.01). During the experimental period there was an increase in plasma Zn levels (p less than 0.005) and in urinary N'MN (p less than 0.05) and 2-PYR (p less than 0.05) excretion in the patients receiving Zn supplementation (group B). These results suggest that Zn interacts with niacin metabolism in alcoholic patients with pellagra through a probable mediation by vitamin B-6.

Hyperzincuria and hypozincemia in patients treated with cisplatin

The effect of cis-diamminedichloroplatinum (DDP) on plasma and urinary zinc was studied in fifteen patients with squamous cell carcinoma. A decrease in plasma zinc accompanied by an increase in urinary zinc excretion was observed. Pretreatment plasma or urinary zinc did not correlate with tumor size or site, nor was there a correlation between changes in these measurements and a response to therapy. The enhanced excretion of urinary zinc may be related to a decrease in amino acid resorption in the proximal tubule. It is concluded that DDP administration may result in hyperzincuria and could potentially precipitate a symptomatic zinc deficiency state.

Nutrient interactions with total parenteral nutrition: effect of histidine and cysteine intake on urinary zinc excretion

Because cysteine and histidine, two amino acids included in total parenteral nutrition regimens, bind zinc and increase its renal ultrafilterability, my objective was to quantify the effects of infusion of amino acids, including cysteine and histidine, on urinary zinc excretion. The effect of the infusion of high amounts of cysteine and no cysteine (100 mg/kg/day vs none) and of high and low amounts of histidine (165 vs. 95 mg/kg/day) on urinary zinc excretion was determined in 14 newborn infants receiving total parenteral nutrition who had similar zinc intakes (approximately 7 mumol/kg/day). After a 72-hour adaptation period, each infant's urine was collected for two 48-hour periods. Urinary zinc excretion during the high-dose histidine and cysteine infusion periods was significantly elevated compared with that during the no-cysteine and low-dose histidine periods. Therefore concurrent intakes of specific amino acids may have to be considered when zinc dosages are calculated.

[A nutrition survey of a group of athletes with particular reference to magnesium, zinc and copper intake, and to the relative intra- and extra-cellular levels]

The aim of the present study was to evaluate the dietary habits in a group of athletes (footballers) compared with sedentary subjects matched for sex, age and body mass index. All subjects kept a record of food eaten for seven consecutive days using various models for portion sizes. Daily nutrient intake was then computed and was expressed as either total intake, or percent of the recommended daily dietary allowances (LARN). For each subject, a 20-ml blood sample and a 24h urine sample was collected for analysis of magnesium, zinc and copper. The three elements were measured both in plasma and in erythrocytes, monocytes and neutrophils. The athletes eat significantly more sheets than controls (22.5% of total kcal vs 15.2%, p less than 0.01) and significantly less cereals (22.5% vs 31.7%, p less than 0.01). Concerning the nutrient composition, in both groups the lipid intake was higher than that recommended and this trend was more pronounced in the athletes (+ 43.2% vs + 16.1% in the controls). In addition, the diet was particularly rich in animal fats with a mean intake of 21.0% of total kcal in the athletes and 20.9% in the sedentary group (recommended value was 12.5% and 14%, respectively). A parallel reduction in vegetal protein intake was observed in the trained group, and the difference was significant (4.3% of kcal in the athletes and 5.2% in the controls, p less than 0.01). Furthermore, in the athletes the soluble carbohydrate intake was higher than the recommended levels (+ 110%) and significantly higher than that eaten by the controls (21.0% vs 16.4% of kcal, p less than 0.01), with parallel decrease of polysaccharides intake.(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary and serum zinc levels in chronic pancreatitis

Urinary and serum zinc levels were determined in 51 patients with chronic pancreatitis. Urinary zinc excretion in patients with chronic calcified pancreatitis (832 +/- 111 micrograms/day) (mean +/- SE) but not in noncalcified pancreatitis (684 +/- 65 micrograms/day) was significantly higher than in normal controls (418 +/- 46 micrograms/day). The urinary zinc excretion increased with deterioration of exocrine pancreatic function. Serum zinc levels in advanced pancreatitis (105.9 +/- 4.5 micrograms/100 ml) were significantly higher when compared to the pancreatitis with normal exocrine pancreatic function (91.6 +/- 3.0 micrograms/100 ml), but the difference was less pronounced than for urinary zinc excretion. This may be due to complicating diabetes, which usually lowers serum zinc. Serum zinc and urinary zinc excretion were low in a patient with chronic calcified pancreatitis complicated with a pulmonary abscess and hypoalbuminemia. In conclusion, urinary and serum zinc levels in chronic pancreatitis were increased as a result of exocrine pancreatic dysfunction. Association of diabetes may lower serum zinc, and associated malnutrition depresses both urinary and serum zinc levels.

Determination and metabolism of dithiol chelating agents. VI. Isolation and identification of the mixed disulfides of meso-2,3-dimercaptosuccinic acid with L-cysteine in human urine

Virtually nothing is known about the biotransformation of the heavy metal chelating agent, meso-2,3-dimercaptosuccinic acid (DMSA). Two fasted, normal, young men were given 10.0 mg DMSA/kg po, and their urines were collected over a 14-hr period. Urine samples were analyzed, before and after electrolytic reductive treatment, for DMSA and its biotransformants using bromobimane derivatization, HPLC separation, and fluorescence detection. Metabolites were isolated by HPLC, ion-pairing extraction, ion-exchange extraction, and TLC. By 14 hr after DMSA administration, 87% of the total DMSA and 95% of the total L-cysteine found in urine consisted of altered forms of these compounds. The urinary excretion of altered DMSA, at 1, 2, 4, 6, 9, and 14 hr after administration of DMSA, when compared to the urinary excretion of altered L-cysteine had a correlation coefficient of 0.952 and p less than 0.003. Approximately 90% of the altered DMSA excreted in the 2- to 4-hr urine was found in disulfide linkage with L-cysteine. The remaining 10% was found as cyclic disulfides of DMSA. Of the mixed disulfides found in 4- to 6-hr urine, 97% consisted of two L-cysteine residues per one DMSA and the remaining 3% consisted of one L-cysteine per one DMSA. The 2:1 mixed disulfides (97%) were isolated as three distinct species by TLC, consisting of 77, 12, and 8% of the total mixed disulfides found. In addition to the novelty of these biotransformants of DMSA, the DMSA-cysteine mixed disulfides indicate a thiol-disulfide interchange between DMSA and L-cystine. The discovery of the formation of these water soluble DMSA-cysteine mixed disulfides should encourage the evaluation of DMSA in the treatment of cystinuria.

Comparison of the antidotal efficacy of polyamincarboxylic acids (CDTA and DTPA) with time after acute zinc poisoning

The effect of increasing the time interval between acute zinc exposure and chelation therapy was studied in male Swiss mice. Cyclohexanediaminetetraacetic acid (CDTA), and diethylenetriaminepentaacetic acid (DTPA) were administered ip at 0, 0.25, 0.5, 2, 12, or 24 hr after ip administration of 0.40 mmol/kg of zinc acetate dihydrate. Chelating agents were given at doses equal to 1/3 of their respective LD50 values. Effectiveness of chelation therapy was determined by measuring the ability of the chelators to increase the elimination of zinc and decrease the concentration of the metal in various tissues. Treatment with DTPA or CDTA increased significantly the urinary and fecal excretion of zinc when the chelators were administered at various times following zinc exposure. The greatest antidotal efficacy of the chelating agents was observed at 0.50 hr after zinc injection. Nevertheless, the effectiveness of DTPA and CDTA was decreasing when the chelators were administered later. DTPA was more effective than CDTA in the prevention of acute zinc intoxication. CDTA would be considered as a possible alternative.

Comparative ability of exogenously administered metals to alter tissue levels and urinary output of copper and zinc

Various metal ions were administered to male Sprague-Dawley rats and their effects on copper and zinc metabolism examined. Of the metals tested, cobalt was unique in producing a substantial (200%) increase in urinary excretion of copper, which lasted through 72 h after a single dose (250 mumol/kg body weight); during the same time period zinc output in urine was markedly (40-50%) reduced. Decreased (approximately 30-40%) renal copper levels were observed following treatment with cobalt, tin, manganese, nickel and iron. Such changes indicate the existence of important biological interactions of exogenously administered metals with endogenous trace elements, and suggest the possibility of utilizing metals such as cobalt to modulate experimentally copper and zinc metabolism.

Copper and zinc status in moderate alcohol intake

To determine the effects of moderate alcohol (ETOH) consumption on dietary intakes, serum and urine zinc (Zn) and copper (Cu) concentrations (conc), groups of nonsmoking, moderate drinkers, non-athletes, healthy young adult males aged 21-35 years and within 10% of ideal body weight, consumed 40g of ETOH/day as beer (fixed group) or maintained normal drinking habits (variable group) for 6 weeks, and then abstained for 3 weeks. A similarly described group of non-alcohol drinkers served as the control. There was no alcohol effect on dietary Zn or Cu intakes, however, the control group had significantly higher intakes of Zn than the drinking groups. Cu intakes were the same in all groups. Generally, the serum Zn and Cu conc of the drinking groups only, markedly rose during ETOH consumption and fell during abstention. Although this trend was not observed in the control group, they had higher serum Zn and Cu conc than the drinking groups. In general, urine Zn conc remained constant from baseline to consumption period and then decreased during the abstention period in all groups studied. Results indicate that moderate ETOH consumption raised serum Zn and Cu conc but had no effect on dietary intakes of these minerals or on urine Zn levels.

The removal of zinc from the mouse by polyamincarboxylic acids (CDTA and DTPA) following semichronic zinc ingestion

Effects of ip treatment with diethylenetriaminepentaacetic acid (DTPA), and cyclohexanediaminetetraacetic acid (CDTA) on the zinc (Zn) excretion and Zn levels in selected mouse organs and tissues were assessed after mice were offered deionized water containing zinc acetate dihydrate (108 mg/kg/day) as the sole drinking fluid for 4 weeks. Following this period, the Zn-containing water was replaced by tap water and therapy with DTPA or CDTA was initiated. The animals received 6 injections of chelators or 0.9% saline (control group) on alternate days for 2 weeks of treatment. The dose of chelating agents was approximately equal to 1/4 of their respective ip LD50 values. Mice were housed in metabolic cages, and urine and feces were collected 24 hr after the first, fourth and sixth administration of the chelators. Six animals in each group were sacrificed at the same days. Although feces was the predominant route of elimination for Zn, only DTPA significantly increased the fecal excretion of Zn after the first administration of chelator. Treatment with DTPA or CDTA resulted in a significant decrease in the concentration of Zn in brain, spleen, and heart after the first injection. DTPA was consistently the most effective in increasing the urinary and fecal excretion of Zn and reducing the concentration of the metal found in various tissues. CDTA would be considered as a possible alternative.

Ratio of post-prostatic massage urinary zinc concentration to initial urinary zinc concentration. An improved method of assessing prostatic function

Various methods have been used clinically to assess prostatic function. We evaluated a number of ways of using zinc in post-prostatic massage urine (VB3) and found that the ratio of VB3 zinc concentration to initial urinary zinc concentration was a good indicator of prostatic secretory activity. This ratio can differentiate hormonally treated patients with carcinoma of the prostate from those untreated and from those with benign prostatic hypertrophy. The specificity is increased for individuals by repeat samples. Comparison of samples before and after resection showed no loss of function and no difference was found between groups treated with orchiectomy or LHRH agonist (Zoladex). The VB3/VB1 zinc concentration could be used in a prospective study of hormonal treatments directed against the prostate, where it could give objective evidence of a fall in secretory function of the gland.

Zinc status in children and young adults with sickle cell disease

Previous studies have suggested an association of zinc deficiency and short stature in some children and adults with sickle cell disease (SCD). As a result, zinc supplementation has been recommended for these patients. The mechanism for zinc deficiency in certain patients with SCD is unknown, although renal loss of zinc has been suggested as a contributing factor. The zinc status of 29 subjects with SCD and 18 black controls was studied. No evidence of zinc deficiency in our population with SCD was found when plasma and cellular zinc levels were measured. Likewise, levels of two zinc-dependent enzymes, alkaline phosphatase and delta-aminolevulinic acid dehydratase, were normal in these subjects with SCD. Although adolescent subjects with SCD tended to be shorter than control subjects, there was no correlation between the height-forage z score and plasma zinc levels (r = -.31). It was concluded that zinc deficiency was not present in our population with SCD, and that there was no correlation between plasma zinc levels and the height-for-age z score in growing adolescent patients with SCD. These findings suggested that zinc supplementation may not be necessary in all patients with SCD.

Hyperzincuria in IDDM women. Relationship to measures of glycemic control, renal function, and tissue catabolism

Eighteen women with insulin-dependent diabetes mellitus (IDDM) and 15 nondiabetic women participated in a study of the relationship of zincuria to measures of glycemic control, renal function, and tissue catabolism. In the IDDM women, mean +/- SE glycosylated hemoglobin was 9.8 +/- 0.5%, and fasting plasma glucose was 189 +/- 19 mg/dl; duration of diabetes averaged 15 yr. In comparison with control women, the IDDM women excreted four times as much zinc in the urine. However, the total plasma zinc concentration was significantly higher in the IDDM than in the control women (14.7 vs. 13.4 microM). The increased urinary zinc loss in the IDDM women was not related to urine volume, urinary glucose excretion, fasting plasma glucose concentration, percent glycosylated hemoglobin, or an increased glomerular filtration rate. Total urinary protein losses were four times higher in the IDDM women than in the control women, and these urinary protein losses correlated with the urinary zinc losses (P less than .007). There was no relationship between urinary zinc and the excretion of any of the amino acids, urea, or ammonia. The results of this study show that hyperzincuria in diabetes is not associated with lower plasma zinc levels. An increased zinc absorption, decreased intestinal zinc excretion, or increased tissue catabolism may support higher plasma zinc levels.

[Determination of zinc and copper in patients with liver cirrhosis of diverse clinical severity]

Zinc and copper levels in the blood and urine of 44 liver cirrhosis patients and 10 healthy volunteers are reported. The clinical severity of the liver disease (according to the Child classification system) was correlated with the levels of the two metals. An attempt was also made to break down the parameters on which the Child System in based in order to contribute to the pathogenic interpretation of changing zinc levels in liver disease patients. The results show a significant reduction in zinc in the blood but an increase in the urine in the various degrees of liver damage. A connection was also noted between low blood zinc and encephalopathy.

Blood and urinary zinc changes after a glucose challenge in early and late pregnancies

This study was undertaken to investigate the effect of pregnancy and glucose loading on zinc metabolism. In a completely random design with repeated measures, 18 non-pregnant women, 16 early-pregnant women (13-17 wk), and 16 late-pregnant women (28-34 wk) had blood collected at 0, 30, 60, 120, and 180 min after ingesting 100 g glucose to evaluate changes in variables of Zn nutriture. Fasting plasma Zn concentrations decreased significantly as pregnancy progressed. Late-pregnant women had significantly higher erythrocyte Zn levels and greater 24-h urinary Zn and glucose excretions. Erythrocyte Zn responses to glucose loading were unaffected by gestational age. Plasma Zn after a glucose load in nonpregnant women exhibited a curvilinear response whereas pregnant women showed no change. This lack of response by pregnant women may be related to their lower plasma Zn concentrations. Plasma Zn in pregnant women may not be as readily available to assist in glucose utilization.

Amino acid intake and urinary zinc excretion in newborn infants receiving total parenteral nutrition

Zinc deficiency is well described in infants on total parenteral nutrition (TPN). Urinary Zn excretion is the major source of Zn loss in the parenterally fed infant; factors causing increased zincuria will predispose the infant to Zn deficiency and affect the recommended Zn intake dosage. Histidine, threonine, and lysine have been shown to bind Zn increasing its renal ultrafilterability. The effect of the infusion of high and low lysine (206 +/- 34 vs 158 +/- 38 mg.kg-1.d-1; means +/- SD), threonine (147 +/- 24 vs 113 +/- 27), and histidine (124 +/- 34 vs 85 +/- 15) on urinary Zn excretion were determined in 23 newborns on TPN who received similar Zn intakes (6.8 +/- 1.4 mumol.kg-1.d-1). After a 72-h adaptation period each infant had urine collected for two 24-h periods. Despite the significant difference in amino acid intakes, mean urinary Zn excretion was identical (1.58 +/- 0.73 vs 1.56 +/- 0.63 mumol.kg-1.d-1). Hyperzincuria, therefore, does not occur when amino acids are infused at rates appropriate for the safety and nutritional maintenance of neonates.

Determination and metabolism of dithiol chelating agents. III. Formation of oxidized metabolites of 2,3-dimercaptopropane-1-sulfonic acid in rabbit

Disulfide metabolites of 2,3-dimercaptopropane-1-sulfonic acid (DMPS), a heavy metal chelating agent, have been found in the urine of catheterized rabbits after a single dose of DMPS. After treating the urine with a reducing agent such as NaBH4, a 20-fold increase in DMPS was observed within 6 hr after administration. This suggested the presence of disulfide metabolites of DMPS. The disulfide metabolites were isolated from urine by extraction and were further purified by ion-interaction reverse phase HPLC. Upon reduction with NaBH4 or dithiothreitol, the isolated disulfides converted to DMPS. The isolated metabolites were not chelates of copper or zinc as determined by atomic absorption. Negative ion fast atom bombardment mass spectra indicated that the isolated metabolites were cyclic and acyclic polymeric disulfides of DMPS. The cyclic polymeric disulfides consisted of dimeric and trimeric forms of DMPS. One of the acyclic polymeric disulfides was identified as a DMPS dimer. Urinary excretion profiles of rabbits revealed that the majority of the altered DMPS consisted of cyclic and acyclic polymeric disulfides of DMPS. The cyclic disulfides increased with time while the acyclic disulfides decreased with time, suggesting that the acyclic forms are intermediates and oxidize to the cyclic forms. The rapid formation of stable 8-membered cyclic dimeric and 12-membered cyclic trimeric disulfides of DMPS strongly suggests that oxidation-reduction reactions are occurring. Both spontaneous and enzymatic oxidation mechanisms appear to be involved.