The value of methods to determine zinc deficiency in patients with Crohn's disease

BACKGROUND

The serum zinc concentration is frequently applied for the assessment of zinc deficiency, but this concentration is also influenced by other factors. The aim of this study was to compare various methods of assessing the zinc status in patients with Crohn' s disease.

METHODS

Serum levels of zinc, serum alkaline phosphatase activity, and zinc in various types of cells were related to factors potentially inducing zinc deficiency: the number of liquid stools, weight loss, bowel resection, and the extent and severity of inflammation.

RESULTS

Thirty-one patients with more or less active Crohn's disease were included. In 68% of these patients the serum zinc concentration was less than the reference level, and it was correlated with the extent of bowel resection and the van Hees Index but not with the Crohn's Disease Activity Index. Serum alkaline phosphatase activity was correlated with bowel resection. Zinc in blood cells was poorly correlated with factors inducing zinc deficiency.

CONCLUSION

A decrease of serum zinc concentration is frequently seen in active Crohn's disease. This study suggests that the determination of zinc in blood cells is not superior to the determination of the serum zinc concentration and serum alkaline phosphatase activity.

Serum alkaline phosphatase activity during zinc deficiency and long-term inflammatory stress

A decrease in serum zinc can be caused by a real zinc deficiency but can also be caused by an apparent zinc deficiency, e.g. in inflammatory stress. The aim of this study was to evaluate the diagnostic power of serum alkaline phosphatase (AP) activity in the discrimination between pathophysiologic states of "real" and "apparent" zinc deficiency. A decrease in serum zinc was induced in growing and adult rats, by providing a diet low in zinc and by causing inflammatory stress. AP activity was determined using reagents low or enriched in zinc. Serum AP was decreased in zinc-deficient adult rats (P < 0.01). In zinc-deficient growing rats AP activity was not different from normal rats but AP activity decreased rapidly. In the same growing rats a significant difference was found in AP activities determined using buffers low and enriched in zinc (P < 0.001) between both groups of rats. After inducing inflammatory stress a decrease in AP activity (P < 0.01) and serum zinc (P < 0.001) was seen during the first few days. After the initial phase of inflammation AP activity normalized, serum zinc showed a rise which after correction for the decrease in serum albumin reached the level of the control rats. A difference in AP activity in buffers low and enriched in zinc was observed only during the first few days after induction of inflammatory stress (P < 0.001). Probably the method of measurement of the difference in enzyme activity, using buffers low and enriched in zinc, can be used as an indication for zinc deficiency in situations with changing AP enzyme concentrations. AP activity is decreased during the initial phase of inflammatory stress due to a decrease in serum zinc.

Zinc exchange by blood cells in nearly physiologic standard conditions

Determination of zinc concentrations in white blood cells has been used to establish zinc deficiency. During pathological conditions changes in zinc concentrations in these blood cells were observed. However, these investigations were hampered by the low amount of zinc in this form per mL blood. Earlier we demonstrated that, in the case of zinc deficiency, the uptake of zinc was increased, using the in vitro exchange of zinc by the various blood cells with extracellular zinc labeled with 65Zn in fairly physiologic conditions. In case of inflammation, no increase in zinc uptake by erythrocytes was seen, indicating that this method probably can be used to differentiate real from apparent zinc deficiency. Only during the first days of the inflammatory process, probably representing the redistribution phase during which zinc moves from the serum to the liver, a small increase in in vitro zinc uptake was seen in mononuclear cells (MNC) and polymorphonuclear cells (PMNC). Earlier papers raised some questions; e.g., is the uptake part of an exchange process and can the efflux of zinc by the cells be measured by the same method; what is the influence of time on the process of zinc uptake; what is the magnitude of the uptake of zinc by the cells compared to the zinc concentration in the cells; and, what is the influence of temperature on the uptake of zinc? In the present study, the influence of incubation time and temperature on the uptake of zinc by human and rat blood cells and on the release of zinc by rat blood cells was studied. At least three phases of uptake of zinc in the various cells were found by varying the incubation time--a fast phase during the first half hour, probably caused by an aspecific binding of zinc on or in the cell membrane; a second fast uptake between 60-330 min, probably caused by an influx of zinc in the cell as part of the exchange process of zinc; and a slow third phase after 5.5 h, in which probably the in- and efflux of the rapidly exchangeable intracellular pool is more or less equilibrated. For mononuclear cells, polymorphonuclear cells, and erythrocytes of rats, the rapidly exchangeable intracellular pool is 40%, 53%, and 10%, respectively, of the total zinc content of the cells. This study is also performed in human cells; in human cells the exchangeable pool of mononuclear cells and erythrocytes is 17 and 3.5% of the total zinc content of the cells, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Zinc uptake by blood cells of rats in zinc deficiency and inflammation

In zinc deficiency, the function of leukocytes is impaired. However, the results of studies on the zinc concentration of blood cells in zinc deficiency are conflicting, probably in part because of technical and analytical problems. The aim of this study was to investigate, under standard conditions, the uptake of 65Zn-labeled zinc by blood cells, taken from zinc-deficient rats and from rats in which an inflammation is induced. In both conditions, the serum zinc concentration is reduced. In clinical practice, this makes it difficult to determine whether the decrease in serum zinc is the result of a real or an apparent zinc deficiency. In stress, like an inflammatory disease, the decrease of zinc reflects an apparent zinc deficiency because of redistribution of serum zinc into the liver and because of decrease in serum albumin concentration. Over 70% of the serum zinc is bound to albumin. Blood cells from zinc-deficient and control rats were isolated using a discontinuous Percoll gradient and incubated under nearly physiological conditions in a 65Zn-containing medium. A significant increase in the in vitro uptake of 65Zn-labeled zinc by the blood cells of zinc-deficient rats was seen: erythrocytes 1.3, mononuclear cells 2.0, and polymorphonuclear cells 2.6 times the control values. During inflammation, no change in 65Zn-labeled zinc uptake by erythrocytes and mononuclear cells was demonstrated after 2 d, although the serum zinc and albumin concentrations were decreased, but a small but significant increase in zinc uptake by polymorphonuclear cells was observed. This study of 65Zn uptake in vitro under standard conditions may prove of value for distinguishing in patients real zinc deficiency from apparent zinc deficiency owing to, e.g., stress, although additional experiments should be performed.

Changes in zinc metabolism after burns: observations, explanations, clinical implications

Zinc in plasma and urine and serum albumin and alpha 2-macroglobulin were measured in 48 patients with burns. Mean total burned surface area amounted to 18%, ranging from 2 to 55%, and mean hospitalization time amounted to 35 days, ranging from 10 to 124 days. All parameters showed a decrease during the first two post-burn days. Minimal values were reached on days 2 and 3 for plasma and urine zinc, and between days 5 and 10 for the proteins. Thereafter, values increased, rapidly for both plasma and urinary zinc, more slowly for albumin and alpha 2-macroglobulin. The ratio R of the total plasma zinc minus the alpha 2-macroglobulin concentration to the albumin concentration is postulated as an indicator for zinc deficiency. From values of R and of the urinary zinc excretion, conclusions can be drawn about various processes of the zinc metabolism that may occur during the acute stage following the thermal accident and during the stages of tissue demarcation and of recovery. These processes are discussed in terms of possible temporary and/or local zinc deficiency. Evidence is presented that zinc administration in only indicated during the final stages of recovery in case of inadequate dietary intake.

Zinc sulphate therapy for Wilson's disease after acute deterioration during treatment with low-dose D-penicillamine

A 30-year-old woman with Wilson's disease was treated with low-dose D-penicillamine. After 12 days, treatment was changed to zinc sulphate because of severe neurological deterioration. The patient subsequently improved within a few days. During a follow-up period of 20 months, the effectiveness of therapy was evaluated by measuring copper and zinc levels in plasma and urine, and by 64Cu-loading tests. We conclude that sulphate therapy may be a satisfactory alternative, even when rapid deterioration occurs in the early stages of D-penicillamine treatment.

Urinary zinc excretion in a patient with burns: a caveat when using bladder catheters in urine zinc studies

The results of a longitudinal study on plasma and urine zinc concentrations in a patient with 68 per cent burns are described. Special attention was paid to possible zinc contamination due to the use of bladder catheters for urine sampling. The course of the plasma and urine zinc concentrations during the first 50 days in hospital was comparable to those reported in the literature. It was shown that surgery was associated with a pronounced rise in urine zinc level, while catheter replacement caused no significant increase in urinary zinc content in this particular patient. However, measurements of zinc content of and zinc release from three types of bladder catheters showed that the two types of latex-based catheters contained about 0.25 per cent zinc, versus 0.01 per cent in the siliconelastomer equivalent. During an 8 h perfusion latex catheters released about 1.2 mumols zinc (2.5 mumols/l). Possible errors in urine zinc determinations due to zinc contamination from catheters are calculated. Recommendations are made for minimizing these errors.

Iodine-129 as a protein label for studies of plasma protein turnover and its measurement with neutron activation analysis

Iodine-129 (t 1/2 = 1.57 x 10(7) y) was used as a protein label for the measurement of the turnover rate of albumin in two human subjects. Plasma samples were assayed for 129I using destructive neutron activation analysis. The experiment entailed an estimated radiation dose of 0.2 muSv to the total body of the subjects. The turnover parameters showed reasonable agreement with literature values. When in a rabbit the catabolism of (129I + 131I)-labeled autologous albumin was followed, the results obtained with both labels agreed well.

Selenium-induced protection against cis-diamminedichloroplatinum(II) nephrotoxicity in mice and rats

The influence of selenium on cis-diamminedichloroplatinum(II) (c-DDP) nephrotoxicity in mice and rats was assessed, using single doses of both compounds. Sodium selenite, 2 mg of selenium per kg, given 1 h before c-DDP, greatly reduced blood urea nitrogen and creatinine levels and morphological kidney damage in both BALB/c mice and Wistar rats, while administration 1 h after c-DDP did not. Liver toxicity of selenium was evaluated by measuring serum glutamic pyruvate transaminase and serum glutamic oxalate transaminase and by routine histology. No liver damage was observed in animals treated with sodium selenite, 2 mg of selenium per kg, and physiological saline or c-DDP. Pretreatment with sodium selenite did not reduce the antitumor activity of c-DDP against MPC 11 plasmacytoma or Prima breast tumor in BALB/c mice. The present results indicate that sodium selenite may provide protection against c-DDP nephrotoxicity, when it is given before c-DDP. Moreover, selenium has an antineoplastic activity against several tumors. The combination of these qualities may open new perspectives in cancer chemotherapy.

Uptake and turnover of(65)Zn in subcellular fractions of brain of rat under normal and zinc-deficient conditions

After a single injection,(65)Zn is slowly taken up by the brain of the rat to a maximum after 7 d, followed by a turnover phase, with a half-time of about 3 wk. In the brain of rats on a zinc-deficient diet, the(65)Zn content in the brain continued to increase up to 30 d after the injection.The uptake and turnover phases in six different subcellular fractions of the brain showed a pattern similar to that of the whole brain in both the control and zinc-deficient rats. There was no internal redistribution of(65)Zn in the brain under conditions of progressive zinc deficiency.The results are discussed in a model for zinc homeostasis in the brain.

Kinetics of copper absorption in zinc-overload states and following the withdrawal of zinc supplement: the role of endogenous zinc status

Zinc (Zn), in therapeutic dosages, has been used to inhibit copper (Cu) absorption in patients with Wilson's disease. A series of experiments were conducted to substantiate the effects of high dosages of Zn on Cu absorption using the experimental animal model. In the first experiment, five groups of mice were fed five different levels of Zn: 6 ppm (basal diet), 30 ppm (control), 750 ppm, 1,000 ppm, and 2,400 ppm, for a period of 35 days. 64Cu-loading test was conducted to measure whole body retention (WBR) of 64Cu at the 10th, 14th, 21st, and 35th day. Results showed that the inhibition of 64Cu absorption by Zn is dose- and time-dependent. However, maximum inhibition occurred in mice fed 1,000 ppm of Zn, and no additional effect was observed in mice fed 2,400 ppm of Zn. In the second experiment, the distribution between the gastrointestinal tract (GIT) and gut-free carcass, of the retained dose of 64Cu, was measured in controls and in the group fed 750 ppm of Zn. While WBR of 64Cu was significantly lower (p less than 0.01) in mice fed 750 ppm of Zn, the distribution of the retained dose was not affected. In the third experiment, a group of mice was fed 30 ppm of Zn for a period of 70 days (control), and a second group was fed 1,000 ppm of Zn for the first 35 days (repletion), after which they were switched to the basal diet (6 ppm) for the following 35 days (depletion). WBR of 64Cu was conducted in intervals throughout the experimental period.(ABSTRACT TRUNCATED AT 250 WORDS)

Trace element uptake in liver cells. 2. Effect of different proteins in the medium on the uptake of copper and zinc by hepatoma cells

Cultured rat hepatoma cells (HTC-cells) were used to study the uptake of copper and zinc from a minimal salt-glucose medium, supplemented with albumin from different species or with ovalbumin. Competitive equilibrium dialysis showed that at low molar ratios of metal/protein (less than 1) the affinity for copper of human and bovine albumin was about equal, but that of dog albumin or ovalbumin was much lower. Only a small difference in affinity for zinc could be detected between human albumin and ovalbumin. Supplementing the medium with the different proteins the rate of copper uptake in the cell at a given molar Cu/protein ratio increased as follows: human albumin congruent to bovine albumin less than dog albumin less than ovalbumin. When the molar Cu/protein ratio was increased, a discontinuity was seen with all three albumin species at a ratio of about 1. In contrast, the zinc uptake mimics that of Cu/ovalbumin, and no discontinuity was observed using different molar Zn/protein ratios. These results indicate that the rate of copper and zinc uptake depends strongly on its affinity for the protein: a low affinity leads to a high uptake. The results suggest further that at physiologic concentrations zinc is taken up by a mechanism different from that for copper.

The effect of pH and lysosomal extract on rat liver metallothionein (Cd-thionein)

Was studied in vitro. The(109)Cd-labeled protein was isolated by gel filtration and incubated with a lysosomal extract from the same source. No degradation was seen when the pH of the incubation medium was 5 or higher, whereas the degradation of Cd-thionein was completed in 2 h at a pH of 4.5. Dissociation of Cd(2+) from thionein, which takes place to a fair extent at a pH below 5, appears necessary before the enzymatic breakdown of the thionein moiety can take place.

Iron, zinc, and copper balance in short bowel patients on oral nutrition

Data are presented of a 5-day balance study for iron, zinc, and copper in seven patients with short bowel syndrome on oral nutrition. The small bowel remnant of these patients varied from 40 to 110 cm (mean 64 cm) and was radiologically normal in all patients. The study was carried out an average 2.7 yr (range 1 to 5 yr) after intestinal resection. Balance materials (diets, urine, and stools) were measured with neutron activation analysis. Mean iron balance was +28.6 mumol/day (+/- 10.6 SD). Mean zinc balance was +5.4 mumol/day (+/- 6.5 SD) and mean copper balance was +1.5 mumol/day (+/- 2.3 SD). These results are comparable to those reported in healthy controls. When taking into account integumentary losses of these substances, the balance of each individual trace element remained acceptable. It is concluded that a satisfying iron, zinc, and copper status can be achieved in patients after an extensive small bowel resection on oral nutrition.

Trace metal uptake in liver cells. 1. Influence of albumin in the medium on the uptake of copper by hepatoma cells

Cultured rat hepatoma cells (HTC-cells) were used to study the transfer of copper from a well-defined medium to and across the cell membrane and particularly the role of albumin in this process. HTC-cells, maintained in a minimal salt-glucose medium, accumulated far more copper than when maintained in the same medium, but supplemented with albumin. In the latter case, the Cu uptake strongly depended on the molar Cu/albumin ratio. The results suggest a role of albumin in the uptake of trace metals. The results indicate the presence of two types of binding sites for copper on the cell membrane. The sites of the first type bind copper very strongly and are probably responsible for the uptake of copper under physiological conditions. Their number was estimated to be about 10(6) per cell. Those of the second type only bind copper when the molar Cu/albumin ratio exceeds a value of about 1, i.e., under extreme, unphysiological conditions. Furthermore, the results suggest a direct interaction of the Cu-albumin complex with these strong binding sites as a first step in Cu uptake processes.

Autoradiographic demonstration of the copper-accumulating tissues in mice with a defect homologous to Menkes' Kinky Hair disease

Mutated Brindled mice have a genetic defect homologous to the human disorder Menkes' or Kinky Hair disease. These animals were used to survey the tissues in which copper accumulates as result of this defect. Heterozygous and unaffected animals were i.p. injected with radio-copper (64Cu). Sites of pathological 64Cu accumulation were visualized by whole body autoradiography. Apart from the tissues already known to accumulate copper, particularly the kidneys, pathological accumulations were also found in a number of other tissues. It is concluded that in Menkes' disease copper accumulates in epithelioid cells.

Influence of dietary molybdenum on the metabolism of intravenously injected radioactive copper in the rat

Control and molybdenum-supplemented rats (Mo rats) were injected i.v. with 64Cu or 67Cu. The distribution of radioactivity over plasma, liver, and kidney, as well as the intracellular distribution in these organs, was studied as a function of time. Compared with control rats, the level of radioactive Cu in the plasma of Mo rats was increased. The results for liver and kidney of Mo rats had to be corrected for a decrease in specific activity of 64Cu; they suggested that the 64Cu release from the liver and the 64Cu uptake in the kidney of Mo rats ran parallel to that in control rats for up to 8 hr; after which, an increase in both organs of the Mo-rats followed. 64Cu in the subcellular particles and in a high molecular weight (MW) protein of the cytoplasma of the organs of Mo rats was increased compared with control rats. In control rats the transport of 64Cu from a 10,000 MW protein to a 30,000 MW protein of the cytoplasma of the kidney seemed to be much slower compared with that of the liver, but Mo had no influence on this process in either liver or kidney.

Changes in the binding of copper in the plasma of molybdenum supplemented rats

After incubating plasma of Mo-supplemented rats (Mo-plasma) with 64Cu only part of it could be removed by dialysis against EDTA or histidine or by treatment with dithiocarbamate; this nondialyzable Cu was shown to be bound to albumin. The maximal amount of 64Cu bound this way equaled the Mo-induced increase in total plasma Cu. After addition of stable Cu, dialysis of Mo-plasma against a histidine solution showed that no extra Cu became tightly bound, suggesting that the 64Cu binding was due to an exchange between added 64Cu and stable Cu already present. Incubating Mo-plasma with Hg compounds prevented 64Cu binding and released stable Cu, indicating that Cu in Mo-plasma was sulfhydryl bound. Part of the Mo in Mo-plasma was freely dialyzable. The remaining part was shown to be SH bound as well. The estimated atomic ratio of SH-bound Cu and Mo was unity. Molybdenum increased the number of SH groups in plasma, and for each Cu atom at least one SH group was calculated to be present.

The use of hydroxy-DL-proline-2-(14)C in the investigation of hydroxyproline metabolism in normal subjects and in patients with renal insufficiency

The metabolism of hydroxyproline was investigated in six healthy subjects and four patients with chronic renal insufficiency (creatinine clearances respectively 40, 10, 7, 2 1/2 ml/min). For this purpose hydroxy-DL-proline-2-(14)C was administered intravenously and the excretion patterns of radio-activity in plasma, urine and expired air (14CO2) were determined. A separation procedure (using thin layer chromatography followed by oxidation with D-amino acid oxidase) made it possible to determine the concentration of hydroxy-L-proline-2-(14)C in the presence of the D-isomer and the degradation products of both. Although the use of a racemic mixture as tracer made conclusions more difficult, it could be shown that in uremic patients the concentration of hydroxy-DL-proline -2-(14)C remained high in the blood for a longer period, the metabolites appeared in the urine later, and the peak respiratory 14CO2 excretion was reached later and was lower than in the healthy subjects. On this basis it was concluded that the metabolism of hydroxyproline is diminished in patients with renal insufficiency.

131I-asialo-alpha 1-acid glycoprotein. Investigation of its use for liver function tests; metabolism in the rat

On intravenous injection into rats, 131I-asialo-alpha 1-acid glycoprotein was rapidly removed from the circulation. Five minutes after injection only a few per cent of the injected dose remained in the plasma and 75 per cent was found to be in the liver, where it could be localized in the hepatocytes. Fifteen minutes after injection, however, the 131I reappeared in the plasma after the labeled protein had been metabolized by the liver. One hour after injection less than 5 per cent of the injected dose remained in the liver. Studies with this material in a series of rats using a gammacamera showed the reproducibility of the the time-activity curves of the liver. In contrast, the unmodified radioactive alpha 1-acid glycoprotein disappeared from the blood at a much slower rate. The disappearance curve of the unmodified alpha1-acid glycoprotein could be fitted with the sum of two exponential curves with half-times of 2.88 H. and 27.3 H., respectively. The 131I-alpha1-acid glycoprotein did not accumulate in any tissue except the kidneys and some of the radioactivity was excreted in the urine. The possible application of 131I-asialo-alpha1-acid glycoprotein and the comparison with other radiopharmaceuticals for liver studies in nuclear medicine are discussed.

Preparation of 131I-asialo-alpha1-acid glycoprotein

Alpha1-Acid glycoprotein (orosomucoid) was prepared from a byproduct of the ethanol plasma fractionation by means of ion-exchange procedures. Immunoelectrophoresis suggested a high degree of purity; the purified protein contained 13.5% sialic acid and 17.8% hexose. The alpha1-acid glycoprotein was modified by removal of sialic acid with neuraminidase (EC 3.2.1.18) followed by iodination with 131I. The purpose of the preparation, its potential use as a pharmacon for liver function studies in nuclear medicine is the subject of further study.

Binders of intravenously administered 65-zinc in rat liver cytoplasm

The fate of an i.v. injected trace dose of 65Zn2+ in the rat, was studied over a period of 10 days after injection. Tissue distributions were determined and a special study was made of 65Zn binders in liver cytoplasm. A total of 6 65Zn-binding fractions were observed in liver cytoplasm with apparent molecular weights of about 113,000, 66,400, 47,400, 29,000, 23,000 and 11,400. A time study showed that 4 hours after the injection the most prominent cytoplasmatic 65Zn binders are the 113,000, 66,400 and 23,000 molecular weight fractions. A tentative identification of the main Zn binders in the six 65Zn fractions is given, using the collected data regarding their apparent molecular weight, time dependent prominence and content of stable Zn.