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.

Effect of tricarballylic acid, a nonmetabolizable rumen fermentation product of trans-aconitic acid, on Mg, Ca and Zn utilization of rats

trans-Aconitic acid has been implicated in magnesium deficiency of ruminants since the 1960s, but recent experiments indicated that much of it can be converted by rumen bacteria to tricarballylic acid (TCBA). Rats were used as experimental models in the studies described here because analogous experiments in ruminants would have been very expensive. When TCBA was fed to young male Sprague-Dawley rats as 2% of an AIN-76A diet with marginal (200 mg/kg) or adequate (500 mg/kg) Mg, virtually all of the dietary acid was recovered in the urine. Mg and Ca absorptions were unaffected by TCBA but urinary losses of Mg, Ca and Zn were higher than in pair-fed controls. TCBA was highly correlated (r = 0.93) with titratable acid excretion, and Mg, Ca and Zn retentions were reduced by 90, 35 and 56%, respectively. Rats fed 2% citric acid, a structurally similar but metabolizable acid, excreted more Zn than controls but did not excrete excess Mg or Ca. Since TCBA led to a depletion of Mg and other cations, it could be a contributing factor in the etiology of the Mg deficiency known as grass tetany in ruminants. Additional work in ruminants now seems warranted.

Serum zinc response in thermal injury

Zinc is an essential trace element required for RNA and DNA synthesis and the function of over 200 zinc metalloenzymes. After surgery or trauma, the serum zinc concentration usually decreases. The magnitude and duration of this hypozincemia after thermal injury are unclear, as are mechanisms for this hypozincemia. In this study we evaluated, over the duration of their hospital course, serum zinc concentrations in 23 thermal injury patients. The initial mean serum zinc concentration was significantly depressed (42 +/- micrograms/dl; normal 66-110 micrograms/dl). By the second week of hospitalization, serum zinc concentrations gradually increased into the normal range in the majority of patients. Mechanisms for this hypozincemia were evaluated. Decreases in the serum zinc concentration did not correlate with increased urinary zinc excretion; thus increased urinary zinc excretion was an unlikely mechanism for the observed hypozincemia. Values for albumin, the major zinc binding protein in serum, generally were inversely correlated with the serum zinc concentration. Thus, hypoalbuminemia could not explain the decreased serum zinc concentration. Certain cytokines such as interleukin-1 are known to cause a decrease in the serum zinc concentration as part of the acute phase response. Therefore, we measured serum C reactive protein concentrations as an indicator of the acute phase response. Thermally injured patients initially had markedly elevated C-reactive protein levels which gradually decreased during hospitalization. We suggest that the initial hypozincemia observed in thermally injured patients may be a reflection of interleukin-1 mediated acute phase response. Whether one should vigorously attempt to correct this initial marked hypozincemia requires further investigation.

Evaluation of zinc status in subjects with Crohn's disease

Zinc status was evaluated in 30 subjects with Crohn's disease. Intestinal resection had previously been performed in 23 of the subjects. The concentrations of zinc were determined in plasma, erythrocytes, percutaneous muscle biopsies, and in urine collected during 24 hours. The results were compared with those in 19 healthy controls. Most of the patients had a normal zinc status. The levels of zinc were, however, reduced (i.e., less than mean -2 SD for controls) in plasma for five, in erythrocytes for two, and in muscle biopsies for six subjects with Crohn's disease. The mean concentrations of zinc in plasma and erythrocytes were reduced (P less than 0.05), whereas the mean content of zinc in muscle biopsies and the mean urinary excretion of zinc were not significantly different, in subjects with Crohn's disease. The various zinc parameters did not correlate to each other. The results indicate that some subjects with Crohn's disease had an intracellular zinc depletion, which, however, was not reflected by a reduction in levels of zinc in plasma.

The influence of ketosis on the metabolic response to skeletal trauma

Intravenous glucose and ketone body feeding were compared for their potential in altering urinary nitrogen losses by the traumatized rat. Eighteen male rats were traumatized by bilateral femoral fracture. The rats were fed totally by vein for 3 days prior and 3 days after injury and the infusion rate was held constant over the 6 days of infusion. Group GT rats were fed glucose as the source of nonprotein energy while group MT rats were fed a mixture of 72% monoacetoacetin (the monoglyceride of acetoacetate)-28% glucose for the nonprotein energy. Total urinary nitrogen excretion on a 24-hr basis was measured for each of the 6 days of intravenous feeding. On the third day post-trauma, each rat was evaluated for leucine kinetics using a continuous infusion of L-[1-14C]leucine and measurement of breath and plasma specific activities. Rats from group MT were hyperketonemic and normoglycemic and rats from group GT were normoketonemic and hyperglycemic. Urinary nitrogen losses, leucine oxidation, and leucine turnover were similar for the two groups. We conclude that ketone bodies are as good an intravenous source of energy as is glucose, and the ketone bodies do not cause hyperglycemia.

Arsenic, selenium, and zinc in patients with Blackfoot disease

Blackfoot disease is a peripheral vascular disease resulting in gangrene of the lower extremities. Extensive epidemiological study implicates that high arsenic content in artesian well water is the responsible causal factor of the disease. In the present study the concentrations of arsenic, selenium, and zinc in the body fluids and hair of patients with Blackfoot disease, in comparison to age- and sex-matched normal controls, are investigated. Two analytical techniques that include atomic absorption spectrometry and neutron activation analysis were used for the analysis of urine, serum, hair, and whole blood. The analytical results indicate that hair arsenic of the patients is significantly higher than that of the controls, but still below the critical value of 1 microgram/g. In addition, the patients showed significantly lower concentrations of Se and Zn in the urine and blood than the normal controls. The possible connection of these elements with the etiology of the disease is discussed.

Influence of dietary picolinic acid on mineral metabolism in the rat

Male rats were fed isonitrogenous, isocaloric diets containing different amounts of dietary zinc and picolinic acid (PA) (25, 60, 120 ppm Zn, 0, 20, 40, 60 mmol PA/kg diet) and balance collections of urine and faeces made over a 4-day period. Rats fed 25 ppm Zn were in negative Zn and Cu balance during the experiment. Faecal Zn, but not urinary Zn excretion was elevated with increasing dietary Zn supply. Urinary Zn, Cu and Mg excretion increased with increasing intakes of dietary PA, regardless of Zn intake. Tissue Zn levels were unaffected by dietary Zn or PA. It is concluded that dietary PA forms soluble complexes with metal ions which are rapidly absorbed but are then re-excreted in urine and may not be available for metabolism or incorporation into tissues.