Copper-deficient Rats Research Articles

Lower Copper, Zinc-Superoxide Dismutase Protein but Not mRNA in Organs of Copper-Deficient Rats

Copper deficiency was induced in Sprague Dawley rats by dietary restriction to confirm and extend studies on copper, zinc-superoxide dismutase (Cu,Zn-SOD). Male rats restricted from copper in two models, a traditional postweanling model examining 50-day-old rats fed a low copper diet for 32 days (postnatal) and a gestational–lactational model examining 23-day-old male offspring of dams started on copper deficiency at day 7 of gestation (perinatal), showed signs of severe copper deficiency including anemia, and cardiac hypertrophy. Compared to control rats, copper-deficient rats exhibited lower copper concentrations in the liver, heart, brain, and kidney and lower Cu,Zn-SOD activity in the same organs with the exception of the brain in the postnatal model. In addition, there was a significant reduction in Cu,Zn-SOD protein detected by Western immunoblot proportional (r = 0.96) to the reduction in Cu,Zn-SOD activity. In the liver the reduction in Cu,Zn-SOD protein was approximately 50%. The reduction in Cu,Zn-SOD protein is likely due to a post-transcriptional mechanism as steady-state Cu,Zn-SOD mRNA levels measured by Northern hybridization were not altered by copper deficiency in any organ studied (liver, heart, and brain). Perhaps apo-Cu,Zn-SOD is degraded faster than fully metal-loaded enzyme. The loss of Cu,Zn-SOD activity and protein reduces the antioxidant defense capacity of copper-deficient organs.

Augmented metalloproteinase activity and acute lung injury in copper-deficient rats.

Dietary copper is required for normal function of >30 mammalian enzyme systems. Copper deficiency causes a number of cardiovascular defects as well as impaired immune cell function. Little is known regarding the effects of copper deficiency on acute inflammatory responses, but this topic is relevant because many members of the Western population receive less than the recommended dietary allowance of copper. In the current studies, we investigated the effects of dietary copper deficiency on acute lung injury induced by intrapulmonary deposition of IgG immune complexes. Weanling male Long-Evans rats were fed diets either adequate (5.6 microg/g) or deficient (0.3 microg/g) in copper. IgG immune complex lung injury was greatly increased in copper-deficient rats as determined by lung vascular leakage of albumin and histopathology. However, no change was observed in either the lung content of tumor necrosis factor-alpha or lung neutrophil accumulation. Lungs from copper-deficient rats had much higher levels of matrix metalloproteinase (MMP)-2 and MMP-9 than did copper-adequate control animals. This increased activity was not attributable to alveolar macrophages or neutrophils. These data suggest that the augmented lung injury caused by copper deficiency is due to increased pulmonary MMP-2 and MMP-9 activity and not a generalized amplification of the inflammatory response.

Isolated ventricular myocytes from copper-deficient rat hearts exhibit enhanced contractile function.

Dietary copper deficiency leads to cardiac hypertrophy, cardiac fibrosis, derangement of myofibrils, and impaired cardiac contractile and electrophysiological function. The purpose of this study was to determine whether impaired cardiac function from copper deficiency is due to depressed contractile function at the single myocyte level. Male Sprague-Dawley rats were fed diets that were either copper adequate (5.59-6.05 microg copper/g body wt; n = 11) or copper deficient (0.29-0.34 microg copper/g body wt; n = 11) for 5 wk. Ventricular myocytes were dispersed and mechanical properties were evaluated using the SoftEdge video-based edge-detection system. Intracellular Ca2+ transients were examined using fura 2-acetoxymethyl ester. Myocytes were electrically stimulated to contract at 0.5 Hz. Properties evaluated included peak shortening (PS), time to peak shortening (TPS), time to 90% relengthening (TR90), and maximal velocities of shortening and relengthening (+/-dL/dt). Myocytes from the copper-deficient rat hearts exhibited significantly enhanced PS values associated with shortened TR90 measurements compared with those from copper-adequate rat hearts. The +/-dL/dt values were enhanced and the intracellular Ca2+ transient decay rate was depressed in myocytes from copper-deficient rats. These data indicate that impaired cardiac contractile function that is seen in copper-deficient whole hearts might not be due to depressed cardiac contractile function at the single cell level but rather to other mechanisms such as cardiac fibrosis.

Leukocyte–endothelial adhesion is impaired in the cremaster muscle microcirculation of the copper-deficient rat

Dietary copper deficiency impairs the function of both the vascular endothelium and circulating leukocytes. In the current study, leukocyte–endothelium adhesion was observed in the in vivo cremaster muscle microcirculation of copper-adequate and copper-deficient rats. Male, weanling Sprague–Dawley rats were fed purified diets that were either adequate (5.6 μg/g) or deficient (0.3 μg/g) in copper. Adhesion was stimulated with the inflammatory mediators tumor necrosis factor-α and bradykinin, and the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine. Intravascular adhesion of leukocytes to the vascular endothelium was significantly attenuated in the copper-deficient group in response to all three agonists. These results occurred without any difference in intravascular wall shear rate between the dietary groups. Based on previous work, we propose that the attenuated response is caused by either decreased expression of adhesion molecules on leukocytes and endothelial cells or by inhibition of the endothelial cell calcium signaling associated with copper deficiency.

Nuclear respiratory factors 1 and 2 are upregulated in hearts from copper-deficient rats.

It is known that mitochondrial transcription factor A (mtTFA) plays a pivotal role in coordinating the expression of proteins in the nuclear and mitochondrial genomes as it pertains to mitochondrial biogenesis. Hearts from copper-deficient rats have elevated mtTFA levels compared to copper-adequate rats. This study evaluated whether two proteins that control activation of mtTFA by binding to its promotor, nuclear respiratory factors 1 (NRF-1) and 2 (NRF-2), are also upregulated prior to any upregulation of mtTFA. Long-Evans male rats were fed either copper-adequate or copper-deficient diets from weanling for periods of time up to 26 d. At d 26, mtTFA levels were elevated in the hearts from the copper-deficient rats, but not at earlier time points of 14, 18, and 22 d. However, NRF-1 and NRF-2 levels were increased at d 14 and 18, but not at the other two later time-points. These results revealed that the upregulation of mtTFA and mitochondrial biogenesis is preceded by upregulation of NRF-1 and NRF-2, which is consistent with the known molecular events controlling mitochondrial biogenesis in other systems.

Anemia is associated with hypercholesterolemia in rats only when liver iron is elevated

The objective of this study was designed to answer the question whether anemia per se is a potential inducer of hyperlipidemia. For this purpose, two types of anemia were induced; copper-deficiency and iron-deficiency anemia. Seventy-two weanling male Sprague–Dawley rats were assigned randomly to 12 dietary groups differing in the levels of copper, iron, and the types of dietary carbohydrates. The rats were fed either a copper-deficient (0.6 μg Cu/g) or adequate (6.0 μg Cu/g) diets containing either low (5), adequate (50), or high (500) μg Fe/g The diets also contained fructose or starch as the sole source of dietary carbohydrate. All iron-deficient rats became anemic. Copper-deficient rats developed anemia only when they consumed the diet containing fructose and when they consumed the high levels of dietary iron. Anemia, per se, was not associated with elevated levels of blood cholesterol or triglycerides unless the diet consumed was deficient in copper and was either high in iron or contained fructose. The most severe hypercholesterolemia developed in rats fed the copper-deficient diet, which contained high levels of iron. These rats also exhibited high levels of liver iron. The highest degree of hypertriglyceridemia developed in copper-deficient rats fed the fructose-based diet. Data show that anemia per se was not associated with hypercholesterolemia. Similarly, excess liver iron by itself was not accompanied with hypercholesterolemia. The combination of anemia with excess liver iron was instrumental in raising blood cholesterol. J. Trace Elem. Exp. Med. 14:81–87, 2001. Published 2001 Wiley-Liss, Inc.

Self-selection of copper-containing diets by copper-deficient and overloaded rats

To determine the effect of copper status on the preference for copper-containing food, male Sprague–Dawley rats were weaned to a copper-deficient, copper-adequate or high-copper diet. Four weeks later, alterations in copper status were confirmed by measurement of liver copper concentrations. Rats ( n=10) were then given the choice between a copper-adequate or a copper-restricted diet of similar composition. Preference scores indicated that control rats preferred copper-deficient food. Preferences of rats on the high-copper diet were not different from control rats, suggesting that copper overload did not alter the pattern of selection. However, 7 of the 10 copper-deficient rats ate 80% or more of their intake as copper-adequate food resulting in preference scores that were significantly different from controls ( p<0.03). This alteration in preference was corrected within 1 day of access to copper-adequate food.

Mitochondrial Transcription Factor A Is Increased but Expression of ATP Synthase β Subunit and Medium-Chain Acyl-CoA Dehydrogenase Genes Are Decreased in Hearts of Copper-Deficient Rats

The mechanism(s) by which impaired mitochondrial respiratory function and the accumulation of lipid droplets and mitochondria in hearts of copper-deficient rats occur remains unclear. It is not known whether specific components of the regulatory pathway involved in mitochondrial biogenesis, such as mitochondrial transcription factor A (mtTFA) and nuclear respiratory factors 1 and 2 (NRF-1 and NRF-2), are activated in copper deficiency. Little is known about gene expression of enzymes involved in fatty acid oxidation (FAO) in hearts of copper-deficient rats. Male weanling rats were fed copper-adequate (CuA), copper-deficient (CuD) or pair-fed (CuP) diets for 5 wk. Mitochondria and lipid droplet volume densities from electron micrographs were greater and there was an elevation in the mtTFA protein level in hearts of copper-deficient rats. DNA binding activities of NRF-1 and NRF-2 did not differ among the groups. Northern blot analysis of cardiac tissue revealed that transcripts of F(1)F(0)-ATP synthase subunit c were greater, but mRNA levels of ATP synthase beta subunit and the FAO enzyme, medium-chain acyl-CoA dehydrogenase (MCAD), were lower in hearts of copper-deficient rats. Long-chain acyl-CoA dehydrogenase (LCAD) mRNA levels did not differ among treatment groups. These results suggest that certain components of the mitochondrial biogenesis program are activated in hearts of copper-deficient rats. F(1)F(0)-ATP synthase beta subunit and MCAD transcript levels remain low, which may contribute to impaired mitochondrial respiratory function, decreased fatty acid utilization and lipid droplet accumulation in hearts of copper-deficient rats.

Intestinal β-carotene 15,15′-dioxygenase activity is markedly enhanced in copper-deficient rats fed on high-iron diets and fructose

The purpose of the present work was to examine effects of the Cu-Fe interaction on intestinal beta-carotene 15,15'-dioxygenase activity when a wide range of dietary Fe (deficiency to excess) was used in relation to Cu status of rats. The effect of dietary carbohydrates was also examined since they play a role in the Cu-Fe interaction in vivo. Weanling male Sprague-Dawley rats (n 72) were divided into twelve dietary groups, which were fed on either low-, normal-, or high-Fe levels (0.9, 9.0, and 90.0 mmol Fe/kg diet respectively) combined with Cu-adequate or -deficient levels (0.94 and 0.09 mmol Cu/kg diet respectively) and with starch or fructose in the diets. The data showed that both Fe concentration and beta-carotene 15,15'-dioxygenase activity in small intestinal mucosa were enhanced with increasing dietary Fe and with Cu deficiency v. Cu adequacy. Dietary fructose did not aggravate the Fe-enhancement, related to Cu deficiency, in the small intestine; however, fructose increased the intestinal dioxygenase activity in rats fed on normal- or high-Fe diets when compared with starch controls. Thus, the highest intestinal dioxygenase activity associated with the lowest hepatic retinol (total) concentration was found in rats fed on the Cu-deficient, high-Fe, fructose-based diet. Finally, a positive linear relationship was found between the dioxygenase activity and Fe concentration in intestinal mucosa. In conclusion, the data indicate that beta-carotene 15,15'-dioxygenase activity requires Fe as cofactor in vivo and the enzyme is modulated by the three dietary components: Cu, Fe, and fructose.

Decreased passive stiffness of cardiac myocytes and cardiac tissue from copper-deficient rat hearts.

Passive stiffness characteristics of isolated cardiac myocytes, papillary muscles, and aortic strips from male Holtzman rats fed a copper-deficient diet for approximately 5 wk were compared with those of rats fed a copper-adequate diet to determine whether alterations in these characteristics might accompany the well-documented cardiac hypertrophy and high incidence of ventricular rupture characteristic of copper deficiency. Stiffness of isolated cardiac myocytes was assessed from measurements of cellular dimensional changes to varied osmotic conditions. Stiffness of papillary muscles and aortic strips was determined from resting length-tension analyses and included steady-state characteristics, dynamic viscoelastic stiffness properties, and maximum tensile strength. The primary findings were that copper deficiency resulted in cardiac hypertrophy with increased cardiac myocyte size and fragility, decreased cardiac myocyte stiffness, and decreased papillary muscle passive stiffness, dynamic stiffness, and tensile strength and no alteration in aortic connective tissue passive stiffness or tensile strength. These findings suggest that a reduction of cardiac myocyte stiffness and increased cellular fragility could contribute to the reduced overall cardiac tissue stiffness and the high incidence of ventricular aneurysm observed in copper-deficient rats.

Plasma Diamine Oxidase Activity Is Greater in Copper-Adequate than Copper-Marginal or Copper-Deficient Rats

The object of this study was to determine whether serum diamine oxidase activity could distinguish among adequate, marginal and deficient copper status in rats. Male weanling Sprague-Dawley rats (n = 21) were randomly assigned to one of three dietary regimens, with copper concentrations of 0.52, 1.73 and 6.7 mg/kg diet. On completion of the study, body weights were significantly different among dietary groups, with copper-marginal rats displaying the highest mean weight and copper-deficient rats the lowest. Copper-deficient rats ate significantly less food than the other two groups. Rats fed the three diets had significantly different liver copper concentrations. Liver and heart superoxide dismutase and cytochrome c oxidase activities, and plasma ceruloplasmin and erythrocyte superoxide dismutase activities were significantly lower in the copper-deficient rats than in the other two groups. Plasma diamine oxidase activity was lower in both copper-deficient (0.18 +/- 0.11 U/L) and marginal (0.21 +/- 0.11 U/L) rats compared with copper-adequate rats (3.35 +/- 0.28 U/L). Of the biochemical indices measured, only liver copper concentration (-20%) and plasma diamine oxidase activity (-94%) differed between rats fed copper-marginal and copper-adequate diets. Plasma diamine oxidase activity, therefore, may be a sensitive functional biomarker of suboptimal copper status.

Endothelial cell calcium mobilization to acetylcholine is attenuated in copper-deficient rats.

Dietary copper deficiency significantly attenuates nitric oxide (NO)-mediated vascular smooth muscle relaxation and vasodilation. There is evidence for both increased inactivation of the NO radical by superoxide anion, and oxidative damage to the endothelium where NO is produced. The current study was designed to examine the NO synthetic pathway in the endothelium during copper deficiency. Male weanling rats were fed a copper-adequate (CuA, 6.4 mg Cu/kg diet) or copper-deficient (CuD, 0.4 mg Cu/kg diet) diet for four weeks. Cremasteric arterioles (approximately 100 microm diameter) were isolated and used for the experiments. Western blot analysis of the arteriole endothelial nitric oxide synthase (eNOS) concentration did not show a difference between dietary groups. Acetylcholine (Ach)-induced vasodilation was significantly reduced in the CuD group both before and after pretreatment with the eNOS substrate L-arginine. Endothelial intracellular calcium ([Ca2+]i) stimulated by 10(-6) M Ach was significantly inhibited in the arterioles from CuD rats. Coincident with the inhibition of [Ca2+]i and vasodilation was a depression of vascular Cu/Zn-SOD activity and an increase in plasma peroxynitrite activity. These data suggest that endothelial Ca2+ signaling and agonist-stimulated NO-mediated vascular dilation are likely reduced by increased oxidative damage in copper-deficient rats.

Copper Deficiency Alters Rat Dopamine β-Monooxygenase mRNA and Activity

Dopamine β-monooxygenase (DBM), a cuproenzyme, converts dopamine to norepinephrine in selected cells. Studies were conducted in albino rats to resolve the known paradox of DBM after copper deficiency in which metabolite analyses of tissues suggest lower activity, whereas direct assay of homogenates suggests enhanced activity. After 4 wk of postweanling copper deficiency, male Holtzman rats exhibited 1.4-fold higher adrenal DBM activity and 1.8-fold higher adrenal DBM mRNA levels than copper-adequate rats. Mixing experiments did not support the existence of endogenous activators or inhibitors. Adrenal catecholamine content indicated lower norepinephrine, higher dopamine and unaffected epinephrine content in copper-deficient compared with copper-adequate rats. Studies in 22-d-old male Sprague-Dawley offspring of dams started on copper deficiency at d 7 of gestation indicated similar results for adrenal DBM mRNA, a 1.75-fold increase compared with copper-adequate pups. Adrenal dopamine content was higher in female copper-deficient offspring compared with controls, but norepinephrine was not lower. Medulla oblongata/pons DBM mRNA concentration was higher in 22-d-old copper-deficient female but not male rats compared with controls. Six weeks of copper repletion to the 22-d-old rats restored adrenal DBM mRNA levels to control values. Enzyme assay and RNA results are consistent with enhanced formation of DBM in adrenal gland and noradrenergic cell bodies of copper-deficient rats. The molecular signal may not be solely lower norepinephrine content because adrenal DBM mRNA changes were evident in both nutritional models, whereas the norepinephrine content was altered only in the postnatal model.

Calcium Reintroduction Decreases Viability of Cardiac Myocytes from Copper-Deficient Rats

Copper deficiency leads to profound cardiac hypertrophy and failure. Myocytes were isolated from hearts of copper-deficient and copper-adequate male Holtzman rats to characterize size and function of the cells. Weanling rats were offered a semipurified diet low in copper in two separate experiments (Experiment 1, 0.45 mg Cu/kg and Experiment 2, 0.30 mg Cu/kg). Control (copper-adequate) rats drank water supplemented with cupric sulfate (20 mg Cu/L). Compared with copper-adequate rats, copper-deficient rats had lower hematocrits, liver copper concentrations and plasma ceruloplasmin activities, and higher heart weights and liver iron concentrations. When myocytes were isolated in low calcium media (1 μmol/L), cell viability was not affected by diet history. However, upon restoration to more physiologic levels of calcium (1 mmol/L), cells from copper-deficient rats were less viable, exhibiting an average loss of 34 and 40% in Experiments 1 and 2, respectively, compared with a 9.5 and 13% loss of cells, respectively, from the copper-adequate rats. Addition of the calcium channel blocker, verapamil, did not block this calcium-dependent loss of viability nor did the mitochondrial calcium channel blockers, ruthenium red and cyclosporin A. For comparison with another model of cardiac hypertrophy, the calcium sensitivity of myocytes from hypertrophic hearts of Sprague-Dawley rats with aortic constrictions was found not to differ from that of sham-operated rats. Thus, cardiac hypertrophy associated with postnatal copper deficiency results in a unique increased calcium intolerance of isolated myocytes.

Level of Dietary Iron, Not Type of Dietary Fat, is Hyperlipidemic in Copper-Deficient Rats

Objective: This study was conducted to determine whether high dietary iron will negate the protective effect of unsaturated fat against hyperlipidemia.Methods: Forty-eight weanling, male Sprague Dawley rats were randomly assigned to eight dietary groups differing in the levels of copper and iron and type of dietary fat (saturated or unsaturated). The diets were either deficient (0.6 μg Cu/g) or adequate (6.8 μg Cu/g) copper and either adequate (53 μg Fe/g) or high (506 μg Fe/g) iron. All diets contained starch as the sole source of dietary carbohydrate.Results: Regardless of the type of dietary fat, three copper-deficient rats fed the high levels of dietary iron died prematurely due to ruptured hearts. Surviving rats belonging to the copper deficiency and high-dietary iron regimen developed severe anemia, enlarged hearts and livers, and exhibited the highest levels of liver iron. These rats also developed hypercholesterolemia. Triglycerides were elevated by the consumption of high iron diets.Conclusion: Data show that levels of dietary iron, not the type of dietary fat, are potential inducers of hypertriglyceridemia. Data also show that the combination of high iron intake and dietary copper deficiency is responsible for elevating blood cholesterol.

β-Carotene 15,15′-Dioxygenase Activity is Responsive to Copper and Iron Concentrations in Rat Small Intestine

Objective: Previous in vitro studies have suggested that β-carotene 15,15′-dioxygenase is an iron-dependent enzyme. However, in vivo, it is difficult to alter iron tissue concentration by varying dietary iron because of homeostatic control. On the other hand, an interaction between iron and copper has been shown, i.e., copper-deficiency results in an increase of iron in rat liver. Therefore, we hypothesized that intestinal iron concentration could be increased by copper-deficiency. Our objective was to examine the effects of iron as affected by dietary copper on β-carotene 15,15′-dioxygenase activity in the small intestine.Methods: Weanling male Sprague-Dawley rats (40 to 45g) were divided into four dietary groups: two copper-adequate groups (6.0 μg Cu/g diet) and two copper-deficient groups (0.6 μg Cu/g) combined with either normal iron (44 μg Fe/g) or high iron (87 μg Fe/g). Iron and copper concentrations were determined by atomic absorption spectrophotometry and the dioxygenase activity by reverse phase HPLC.Results: Intestinal copper concentration was significantly reduced (40%) by the consumption of the copper-deficient diets, but intestinal iron was not changed by doubling dietary iron in rats fed either copper-adequate or copper-deficient diets. However, as hypothesized, the two copper-deficient groups exhibited higher intestinal iron concentration (≥137%, p<0.001) than the copper-adequate controls. In addition, intestinal β-carotene 15,15′-dioxygenase activity was increased by 27% and 106%, respectively, for copper-deficient rats fed either normal or high iron diets, compared to the respective copper-adequate controls (p<0.01). The dioxygenase activity was not significantly affected by dietary iron in either copper-adequate or copper-deficient groups. Finally, the enzyme activity was positively correlated (r=0.67, p<0.0001) with iron concentration and negatively correlated (r=−0.49, p<0.01) with copper concentration in small intestine.Conclusions: Intestinal β-carotene 15,15′-dioxygenase may be an iron-dependent enzyme sensitive to copper status in vivo.

Folate and homocysteine metabolism in copper-deficient rats

To investigate the effect of copper deficiency on folate and homocysteine metabolism, we measured plasma, red-cell and hepatic folate, plasma homocysteine and vitamin B-12 concentrations, and hepatic methionine synthase activities in rats. Two groups of male Sprague–Dawley rats were fed semi-purified diets containing either 0.1 mg (copper-deficient group) or 9.2 mg (control group) of copper per kg. After 6 weeks of dietary treatment, copper deficiency was established as evidenced by markedly decreased plasma and hepatic copper concentrations in rats fed the low-copper diet. Plasma, red-cell, hepatic folate, and plasma vitamin B-12 concentrations were similar in both groups, whereas plasma homocysteine concentrations in the copper-deficient group were significantly higher than in the control group ( P<0.05). Copper deficiency resulted in a 21% reduction in hepatic methionine synthase activity as compared to the control group ( P<0.01). This change most likely caused the increased hepatic 5-methyltetrahydrofolate and plasma homocysteine concentrations in the copper-deficient group. Our results indicate that hepatic methionine synthase may be a cuproenzyme, and plasma homocysteine concentrations are influenced by copper nutriture in rats. These data support the concept that copper deficiency can be a risk factor for cardiovascular disease.

Early and advanced glycation end-products are increased in dietary copper deficiency

The hypothesis that nonenzymatic glycosylation of proteins (glycation) contributes to damage associated with dietary copper deficiency has depended largely on indirect evidence. Thus far, the observation of an elevated percentage of glycated hemoglobin in copper-deficient rats has provided the only direct evidence of an increase in glycation. We sought further direct evidence of increased glycation in copper deficiency. Male weanling rats were fed a copper-adequate (CuA, 6.4 mg Cu/kg diet) or copper-deficient diet (CuD, 0.4 mg Cu/kg diet) for 5 weeks. Rats fed the CuD diet were copper deficient as judged by depressed organ copper concentrations and a variety of indirect indices. Measurements of hemoglobin A 1 and serum fructosamine (both early glycation end-products) as well as serum pentosidine (an advanced glycation end-product) indicated that all three compounds were elevated in CuD rats relative to CuA rats. This finding further supports the view that glycation is enhanced and thus may contribute to defects associated with dietary copper deficiency.

Heart Murmurs, Valvular Regurgitation and Electrical Disturbances in Copper-Deficient Genetically Hypertensive, Hypertrophic Cardiomyopathic Rats

Objective: Rats with a genetic tendency to develop hypertensive, hypertrophic cardiomyopathy were fed copper-deficient diets and their cardiac responses were investigated.Methods: Five male weanling rats of the Long-Evans and SHHF/Mcc-facp strains were randomly selected to receive diets containing either adequate quantities of copper (94.5 μmol Cu/kg diet) or reduced quantities of copper (<15.8 μmol Cu/kg diet) for 6 weeks, (n=5 within each group). Echocardiograms and electrocardiograms were recorded and analyzed at the end of the 6-week interval.Results: Electrocardiograms from copper deficient groups showed longer Q-T intervals and increased QRS amplitudes than controls. Both the copper deficient and control SHHF groups demonstrated significant QRS complex prolongation compared to Long-Evans rats. Echocardiography analysis showed significant increases in left ventricular area, free wall dimension, and myocardial cross-sectional areas in rats fed a copper deficient diet. The frequency of systolic cardiac murmurs increased in copper deficient rats and were related to the presence of valvular regurgitation as determined from echocardiography.Discussion: However, the data do not suggest that a copper-deficient diet fed to a strain of rats genetically susceptible to heart disease later in life, hastens or worsens the onset of cardiac disease. The genetic predisposition and copper-deficient states exert independent effects upon the heart.

Copper and signal transduction: platelets as a model to determine the role of copper in stimulus-response coupling.

Platelets from copper-deficient rats have been used as a model to investigate the role of copper in receptor-mediated cellular responses. Copper deficiency doubles the rate of dense granule secretion and increases myosin association with the platelet cytoskeleton following thrombin stimulation. Mechanisms underlying the effects of copper deficiency on thrombin-induced signals that elicit dense granule secretion involve suppression of protein kinase C activity and impairment of Ca2+ release from intracellular stores. Copper deficiency also reduces the cellular GTP content of platelets. This may limit receptor effector coupling through GTP-dependent regulatory proteins leading to protein kinase C activation and the release of Ca2+ from intracellular stores. The reduction in GTP content during copper deficiency results from its utilization to maintain cellular ATP levels in response to severely inhibited cytochrome c oxidase activity in platelet mitochondria. Thus, the role of copper in maintaining normal signal transduction may be indirectly related to its biological function in mitochondria.