The biological regulation of copper homeostasis in the rat

Zinc supplementation for four months does not affect plasma copper concentration in infants

AIM

The aim of the present study, which was undertaken as a sub-study within a randomized controlled trial of zinc supplementation, was to evaluate the effect of prolonged zinc supplementation on copper status as assessed by hematological markers.

METHODS

Plasma copper and zinc were estimated at baseline and after 120 d of supplementation in a randomly selected infant subset (115) of the children. Of these, 61 children were in a zinc group (Z) getting 10 mg of elemental zinc, and 54 were in a control group (C) getting supplement without zinc.

RESULTS

Baseline plasma zinc was comparable in the two groups; post-supplementation zinc was significantly higher (Z 93.0 +/- 3.6 vs C 60.6 +/- 8.0) in the zinc supplementation group. There was no significant difference in the mean/median copper levels between the zinc and control groups. The percentage of children with plasma copper <100 microg/dl was also not significantly different between groups (baseline Z 14.8%, C 11.1%; post-supplementation Z 18.0%, C 11.1%). There were no differences between the zinc and control groups after 120 d of supplementation in hemoglobin (Hgb), mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC), or number of lymphocytes or granulocytes.

CONCLUSION

Zinc supplementation of 10 mg/d for 4 mo in this study did not affect copper status, as assessed by plasma copper concentration and hematological parameters, diagnostics of copper deficiency.

Processing of TRH precursor peptides in rat brain and pituitary is zinc dependent

The enzymes responsible for the posttranslational processing of precursor proteins to form alpha-amidated peptide hormones require the availability of several cofactors, including zinc, copper and ascorbate ions. Major changes in the availability of these cofactors, as well as the rate of hormone precursor conversion to active hormone, occur during neonatal development, aging and caloric restriction. The effects of 6 weeks of a zinc-deficient (ZD1) diet, pair feeding (PF) and partial zinc deficiency (ZD6) compared to a control diet on the enzymatic cleavage and processing of prepro-TRH to form TRH have been studied in the hypothalamus, brain, and pituitary of young adult male Sprague-Dawley rats. Reverse phase high pressure liquid chromatography (HPLC) revealed that TRH was the major TRH-IR component of the hypothalamus, brain and pituitary. The effect of zinc deficiency on the TRH-Gly-IR HPLC profile of rat brain was to reduce selectively the are of the peaks for TRH-Gly and other low molecular weight pro-TRH peptide fragments with a C-terminal Gly compared to the corresponding TRH-Gly-IR peaks of the control group. We conclude that the processing of prepro-TRH to form TRH is zinc dependent via posttranslational processing enzymes such as carboxypeptidase H.

The effect of "Ferrodex", vitamin A and "Rovimix beta-carotene" on the iron and copper levels in blood plasma of calves

The effect of Ferrodex, vitamin A and synthetic beta-carotene on the content of iron and copper in the blood serum has been investigated in three groups of calves: I control group without vitamin supplements, II group received only once with the first colostrum dose 1.5 million IU of vitamin A, III group received Rovimix beta carotene containing 10 per cent of the synthetic beta carotene with Mlekomix from the 21st day to the 13th week of life. Moreover half of the calves from each group received Ferrodex intramusculary. Content of iron, total iron binding capacity by serum proteins, level of indirect and direct copper as well as the content of ceruloplasmin were determined in the blood serum of calves. Moreover hematocrit and hemoglobin content in the blood were determined. The results obtained show that a triple intramuscular injection of Ferrodex caused an increase of the level of iron, copper and ceruloplasmin in the blood serum of calves. However, a single administration of vitamin A to the calves or a continuous administration of Rovimix beta-carotene decreased significantly the level of iron and ceruloplasmin copper in blood serum as well as caused a more dynamic ceruloplasmin synthesis with a simultaneous increase in its utilization.

Hepatic zinc, copper, and iron in the developing turkey embryo and newly hatched poult

The ontogeny of hepatic tissue growth and trace metal deposition was examined in the developing turkey embryo and newly hatched poult. Hepatic concentrations of zinc and iron in the embryo declined by about twofold between day 16 of incubation and hatching. Hepatic copper concentration increased approximately fourfold by day 23 of incubation and then declined rapidly through hatching. During the post-hatching period, hepatic zinc concentration increased twofold by day 10, whereas a small increase in hepatic iron concentration occurred just prior to hatching and continued through the third day post-hatching. A significant positive correlation existed between hepatic zinc and iron concentrations in the developing embryo. The concentrations of both these metals were inversely correlated with hepatic copper concentration during the same time. Total hepatic zinc and iron content increased throughout the entire time studied, whereas total copper content increased up to hatching and then declined during the first week post-hatching. The most rapid phase of hepatic metal accretion differed for each metal, with zinc being rapidly accumulated during the post-hatching period, copper during the last half of incubation and iron at about the time of hatching and the first few days post-hatching. Each of these metals demonstrated a specific relationship to hepatic tissue growth that changed between the embryonic and neonatal periods of development.

Copper response to rheumatoid arthritis

Rheumatoid arthritis can be divided into two syndromes, one a potassium deficiency, the other an inappropriate copper requirement seriously affecting the elastin tissues through reduced lysyl oxidase cross linking. The malfunction in copper may arise from the steroids which regulate potassium, which reduces those steroids, and through that, increases the copper response to the needs of the immune system. It is a mechanism which may have evolved to help fight potassium wasting infections.

A possible role for copper-mediated oxidation of thiols in the regulation of the release of luteinizing hormone releasing hormone from isolated hypothalamic granules

A role for copper in the release of luteinizing hormone releasing hormone (LHRH) from hypothalamic neurons has been previously proposed. To elucidate further the mechanism of action of copper, we addressed two questions: (a) what is the active form of copper that interacts with the LHRH granule (ionic or chelated)? and (b) is copper-stimulated LHRH release a result of an interaction of copper with thiol groups and, if so, does it require oxygen? Granules were isolated from hypothalami of adult male rats and were then incubated at 37 degrees C for 3-5 min in a buffered medium. When granules were incubated with various copper complexes, CuATP stimulated LHRH release by 45 +/- 4% (mean +/- SE), copper tartrate by 44 +/- 4%, CuBSA by 27 +/- 7%, and copper histidine by 16 +/- 6%. Neither CuEDTA nor CuCl2 stimulated LHRH release. CuATP-stimulated LHRH release from granules incubated under N2 was 50% of that incubated under air. Furthermore, the CuATP-stimulated release of LHRH was completely inhibited by dithiothreitol or glutathione (10(-3) M each), partially (40-50%) by iodoacetate or 5,5-dithiobis-(2-nitrobenzoic acid), and not at all by oxidized dithiothreitol. Thus, chelated copper, rather than ionic copper, is the active form of the metal, and the action of copper involves an oxidation reaction and granule thiol groups. The precise mechanism of action of copper, however, has yet to be elucidated. We propose that copper may affect LHRH release as follows: copper, bound to an intracellular chelator (protein, peptide, or amino acid), oxidizes thiols of the LHRH granule, leading to a change in granule-membrane permeability and hence to LHRH release.