Protective effect of magnesium supplementation on experimental 3-methyl cholantrene-induced fibrosarcoma and changes in tissue magnesium distribution during carcinogenesis in rats

In this study, we wanted to examine the effect of magnesium (Mg²⁺) supplementation on the experimental 3-methyl cholantrene (3-MC)-induced fibrosarcoma and alterations in (Mg²⁺) distribution in several tissues of the rats, during carcinogenesis. It was determined that serum and tissue (Mg²⁺) levels of the rats in (Mg²⁺)-supplemented diet group were higher than those of the rats in the (Mg²⁺)-nonsupplemented and control groups. The mean time of fibrosarcoma development for (Mg²⁺)-supplemented group was longer than (Mg²⁺)-nonsupplemented group (p<0.05). Symptoms of hypermagnesemia were not observed in any of the rats. These results suggests that dietary (Mg²⁺) supplementation may have a partial anticarcinogenic effect on experimental 3-MC-induced fibrosarcoma by prolongation of the latent period of carcinogenesis.     

补镁对大鼠血管钙化的影响

目的:在大鼠血管钙化模型上,观察外源性补充硫酸镁对大鼠血管钙化的影响,以探讨硫酸镁在血管钙化中作用及机制。方法:用维生素D3加尼古丁诱导大鼠血管钙化,von Kossa染色、钙含量测定及碱性磷酸酶活性测定判断血管钙化程度;用半定量RT-PCR方法测定血管钙化标志分子骨桥蛋白mRNA水平;用生物化学方法测定血管一氧化氮(NO)、超氧化物歧化酶(SOD)和丙二醛(MDA)含量。结果:钙化组大鼠血压升高,收缩压较对照组高27%(P<0.05);血管von Kossa染色见血管中膜弹性纤维间可见大量棕黑色颗粒沉积,主动脉钙含量及碱性磷酸酶活性分别较对照高3.9倍和3.4倍(P<0.01),钙化血管组织骨桥蛋白mRNA表达上调40%(P<0.01),血管钙化后可加重血管组织过氧化损伤;而诱导钙化后外源性补充硫酸镁可减轻血管钙化程度,与钙化组比较,低、高剂量硫酸镁组均明显缓解上述指标的变化。结论:诱导血管钙化后外源性补充硫酸镁可以减轻大鼠血管钙化和血管损伤程度。     

Effect of zinc deficiency and supplementation on lipid peroxidation of renal tissue in ovariectomized rats

The aim of this study was to investigate how zinc deficiency and supplementation affects lipid peroxidation in the renal tissue in ovariectomized rats. Four study groups were formed with 10 Spraque-Dawley rats each. Two of the groups served as normal and ovariectomized controls; the other two were ovariectomized rats that were zinc deficient and zinc supplemented, respectively. The zinc-deficient ovariectomized rats showed greater renal and plasma lipid peroxidation, as indicated by higher malondialdehyde levels than all other groups (p<0.05). These values were higher in the ovariectomized controls than those of the normal controls and of the ovariectomized, zinc-supplemented groups (p<0.05), which, in, turn, showed no significant differences of their respective renal and plasma malondialdehyde values. The renal and erythrocyte glutathione levels in the zinc-supplemented rats were higher than those in all other groups (p<0.05). The zinc-deficient group had the lowest renal and erythrocyte glutathione levels (p<0.05). The renal tissue zinc levels in the ovariectomized rats were higher than those in the zinc-deficient animals, but lower than in the normal controls and zincsupplemented rats (p<0.05). The zinc-supplemented animals had the highest renal tissue zinc levels (p<0.05). The results of this study suggest that zinc deficiency increases renal tissue damage in ovariectomized rats and that zinc supplementation can be used to prevent this condition.     

Daily magnesium supplementation on serum and urinary magnesium changes in rats during prolonged restriction of motor activity

The objective of this investigation was to determine whether a plentiful magnesium (Mg²⁺) supplementation might be used to normalize or prevent Mg deficiency. This is manifested by increased rather than decreased serum Mg²⁺ concentration as is observed during prolonged hospitalization, which is developed during prolonged hypokinesia (HK) (decreased motor activity). Eighty male Wistar rats with an initial body weight of 370–390 g were used to perform the studies: They were equally divided into four groups:

1. Unsupplemented control animals (UCA);
2. Supplemented control animals (SCA);
3. Unsupplemented hypokinetic animals (UHA); and
4. Supplemented hypokinetic animals (SHA).

For the simulation of the hypokinetic effect, the hypokinetic animals were kept in small individual cages made of wood, which restricted their movements in all directions without hindering food and water intake. The control and hypokinetic supplemental animals receive 0.9 mg/mL Mg sulfate daily with their drinking water. Prior to and during the experimental period, urinary excretions of Mg, calcium, and phosphate along with their concentrations in serum, water intake, and urine excretion, and body weight were determined in the control and hypokinetic animals. In the supplemental and unsupplemental hypokinetic rats, urinary excretions and serum concentrations of electrolytes increased significantly, whereas serum concentration and urinary excretion thereof remained unchanged in the supplemented and unsupplemented control animals. It was concluded that a daily intake of large amounts of Mg supplementation cannot be used to prevent or normalize Mg deficiency in rats during prolonged exposure to HK.     

Effect of desmethylimipramine on tissue distribution and anorectic activity of chlorphentermine in rats

The anorectic effect and tissue distribution of chlorphentermine (CP) have been measured in the presence and absence of desmethyl-imipramine (DMI) in rats, following the finding that DMI was a potent displacer of CP from lung tissue in vitro. CP (10 mg/kg) produced significant anorexia for 4–5 hours after intraperitoneal administration and reduced food intake in a manner similar to that of fenfluramine; that is, CP decreased the rate of eating without affecting onset of eating. DMI caused dose-related changes in CP-induced anorexia; 5 mg/kg DMI inhibited the effects of CP (10 mg/kg) while, with 7.5 mg/kg DMI, there was potentiation. DMI (7.5 mg/kg) significantly (P<0.05) decreased CP (10 mg/kg) concentrations in lung tissue and increased concentrations in brain, liver and blood for up to four hours after treatment, but did not affect kidney or skeletal muscle levels. The CP tissue concentration-time profiles for liver, brain and kidney were significantly different in the presence and absence of DMI, suggesting non-linear kinetics, probably due to saturable tissue binding. Using a simple model to describe eating behaviour, the increased anorexia was found to be linearly related to the higher brain levels of CP seen in the presence of DMI.     

Effect of exercise training on in vivo lipolysis in intra-abdominal adipose tissue in rats

Intra-abdominal obesity is associated with cardiovascular disease and non-insulin-dependent diabetes mellitus, and physical training has been suggested to alleviate these conditions. We compared epinephrine-stimulated lipolysis in vivo in three intra-abdominal adipose tissues (ATs: retroperitoneal, parametrial, and mesenteric) and in subcutaneous AT, and we also studied the effect of physical training. Moreover, we studied the effect of physical training on epinephrine-stimulated lipolysis in muscle in vivo. Female rats were either swim trained (15 wk, n = 8) or sedentary (n = 7). Under anesthesia, a two-stage intravenous epinephrine infusion (60 min of 80 and 200 ng. kg(-1). min(-1), respectively) was carried out, and local interstitial glycerol concentration was measured by the microdialysis technique. Blood flow was measured by microspheres. Training increased blood flow in all ATs [on average: 73 +/- 12 (trained) vs. 14 +/- 4 (sedentary) ml. 100 g(-1). min(-1), P < 0. 05]; nevertheless, epinephrine-stimulated interstitial glycerol concentrations were increased or unchanged. Interstitial glycerol concentration was higher in intra-abdominal than in subcutaneous AT in both trained and sedentary rats. In skeletal muscle, interstitial glycerol concentration and blood flow did not differ between trained and sedentary rats. In conclusion, in vivo lipolysis is higher both in the basal state and during epinephrine-stimulation in intra-abdominal than in subcutaneous AT, and training may be beneficial in alleviating intra-abdominal obesity by enhancing lipolysis in intra-abdominal fat depots.     

Effect of long-term swimming exercise on zinc,magnesium, and copper distribution in aged rats

Trace element content of different tissues might be altered by both age and exercise training. We aimed to determine the effects of a 1-yr swimming protocol (60 min/d, 5 day/wk) on tissue levels and the distribution of zinc (Zn), magnesium (Mg), and copper (Cu) in aging rats. Three groups were formed: sedentary and trained old groups and a young control group. Tissue Zn, Mg, and Cu concentrations were measured in the kidney, heart, liver, lungs, and gastrocnemius and soleus muscles. Kidney zinc concentration significantly decreased in the sedentary old group compared to the young control group (p<0.01) and was significantly higher in the trained old group compared to the sedentary old group (p<0.01), whereas Zn levels in the soleus muscle significantly increased in the sedentary old group in comparison to young controls (p<0.05). Tissue Mg concentrations remained unchanged. The sedentary old group exhibited a significant decrease in kidney Cu concentration compared to the young control group (p<0.01). Although kidney Cu levels also decreased in trained old rats in comparison to young controls (p<0.05), they were significantly higher than in sedentary old rats (p<0.01). The decrease in kidney Zn and Cu content as a result of aging was partly prevented by long-term swimming exercise.     

Effect of cadmium on tissue glutathione and glutathione peroxidase in rats: influence of selenium supplementation.

Administration of cadmium (2.5 mg/kg, sc on alternate days for 3 weeks) to male albino rats led to significant accumulation of cadmium and metallothionein in the liver and kidneys. The activity of glutathione peroxidase was significantly decreased whereas, the concentration of glutathione was increased in these organs. Glycine-l-14C incorporation studies showed enhanced synthesis of glutathione in kidney but not in the liver. Selenium supplementation (1 mg/kg/day orally) failed to prevent these cadmium-induced changes, although it resulted in very high accumulation of selenium in these organs indicating the formation of cadmium-selenium complex.     

Effect of oral magnesium supplementation on experimental pre-eclampsia induced by prolonged blockade of nitric oxide synthesis in pregnant rats

Nitric oxide inhibitor L-NAME when given alone caused a significant rise in both systolic and diastolic pressure, an increase in 24 hr urinary protein excretion and reduction in weight of the litter as compared to control group. Supplementation of MgSO4 at lower dose (250 mg/kg) did not inhibit this pre-eclamptic effect of L-NAME; but in higher doses (500 and 750 mg/kg), it inhibited the pre-eclamptic action of L-NAME. The results suggest that administration of MgSO4 improves the foetal outcome and significantly prevents the development of symptoms of pre-eclampsia like hypertension and proteinuria.     

Effect of exercise training on in vivo insulin-stimulated glucose uptake in intra-abdominal adipose tissue in rats

Intra-abdominal obesity may be crucial in the pathogenesis of the insulin-resistance syndrome, and training may alleviate this condition. We compared insulin-mediated glucose uptake in vivo in three intra-abdominal adipose tissues (ATs; retroperitoneal, parametrial, and mesenteric) and in subcutaneous AT and also studied the effect of training. Rats were either swim trained (15 wk, n = 9) or sedentary (n = 16). While the rats were under anesthesia, a hyperinsulinemic ( approximately 900 pM), euglycemic clamp was carried out and local glucose uptake was measured by both the 2-deoxy-D-[(3)H]glucose and microdialysis techniques. Blood flow was measured by microspheres. Upon insulin stimulation, blood flow generally decreased in AT. Flow was higher in mesenteric tissue than in other ATs, whereas insulin-mediated glucose uptake did not differ between ATs. Training doubled the glucose infusion rate during hyperinsulinemia, in part, reflecting an effect in muscle. During hyperinsulinemia, interstitial glucose concentrations were lower, glucose uptake per 100 g of tissue was higher in AT in trained compared with sedentary rats, and training influenced glucose uptake identically in all ATs. In conclusion, differences between ATs in insulin sensitivity with respect to glucose uptake do not explain that insulin resistance is associated with intra-abdominal rather than subcutaneous obesity. Furthermore, training may be beneficial by enhancing insulin sensitivity in intra-abdominal fat depots.     

Effects of histidine on tissue zinc distribution in rats

Histidine has been reported to affect body zinc status by increasing urinary zinc excretion. The effects of experimental histidinemia on distribution of⁶⁵Zn in anesthetized rats were studied. Infusion ofl-histidine at a rate sufficient to raise plasma concentrations to approximately 2mm for 6h starting 48 h after a single intraperitoneal⁶⁵Zn injection did not alter⁶⁵Zn activities in a variety of tissues when compared with anesthetized uninfused animals. However, plasma⁶⁵Zn and erythrocyte⁶⁵Zn were decreased, and liver⁶⁵Zn was increased. If⁶⁵Zn was injected intravenously during histidine infusion, net accumulation of zinc by some tissues was increased, but uptake by others was reduced relative to uninfused animals. In all cases, however, uptake expressed relative to plasma⁶⁵Zn levels was increased when allowance was made for the more rapid fall in plasma⁶⁵Zn during histidine infusion. Similar infusions ofd-histidine produced quantitatively similar effects. Since enzymatic mechanisms and amino acid carriers would be expected to show stereoselectivity, such processes are unlikely to be involved in the zinc distribution changes described. The possibility of zinc transport by a hitherto unidentified carrier is discussed. These experiments confirm that histidinemia can affect zinc status, but any associated changes in urinary zinc excretion do not seem adequate to account for the tissue changes found.     

Effect of dietary supplementation with selenium-enriched yeast or sodium selenite on selenium tissue distribution and meat quality in commercial-line turkeys

The objective of this study was to determine the concentration of total selenium (Se) and proportions of total Se comprised as selenomethionine (SeMet) and selenocysteine (SeCys) in the tissues of female turkeys offered diets containing graded additions of selenized-enriched yeast (SY), or sodium selenite (SS). Oxidative stability and tissue glutathione peroxidase (GSH-Px) activity of breast and thigh muscle were assessed at 0 and 10 days post mortem. A total of 216 female turkey poults were enrolled in the study. A total of 24 birds were euthanized at the start of the study and samples of blood, breast, thigh, heart, liver, kidney and gizzard were collected for determination of total Se. Remaining birds were blocked by live weight and randomly allocated to one of four dietary treatments (n = 48 birds/treatment) that differed either in Se source (SY v. SS) or dose (Con [0.2 mg/kg total Se], SY-L and SS-L [0.3 mg/kg total Se as SY and SS, respectively] and SY-H [0.45 mg total Se/kg]). Following 42 and 84 days of treatment 24 birds per treatment were euthanized and samples of blood, breast, thigh, heart, liver, kidney and gizzard were retained for determination of total Se and the proportion of total Se comprised as SeMet or SeCys. Whole blood GSH-Px activity was determined at each time point. Tissue GSH-Px activity and thiobarbituric acid reactive substances were determined in breast and thigh tissue at the end of the study. There were responses (P < 0.001) in all tissues to the graded addition of dietary Se, although rates of accumulation were highest in birds offered SY. There were notable differences between tissue types and treatments in the distribution of SeMet and SeCys, and the activity of tissue and erythrocyte GSH-Px (P < 0.05). SeCys was the predominant form of Se in visceral tissue and SeMet the predominant form in breast tissue. SeCys contents were greater in thigh when compared with breast tissue. Muscle tissue GSH-Px activities mirrored SeCys contents. Despite treatment differences in tissue GSH-Px activity, there were no effects of treatment on any meat quality parameter.     

Effect of selenium supplementation on polyunsaturated fatty acids in rats

The purpose of this work was to study plasma, adipose tissue, and liver fatty acids percentages of Wistar rats that drank water supplemented with several levels of sodium selenite for 1, 3, and 6 mo. In a general way, percentages of saturated, monounsaturated, and polyunsaturated fatty acids of supplemented groups were not different from those obtained with nontreated animals in the analyzed tissues. However, in rats supplemented with 0.5 ppm Se, mainly in adipose tissue, a polyunsaturated fatty acids increase (p<0.005) was observed for all times of treatment. This could suggest that 0.5 ppm Se supplement probably exercises a protective role on polyunsaturated fatty acids in that tissue. Supplements of 6.0, 15.0, and 54.0 ppm Se did not change unsaturation levels of fatty acids in the analyzed tissues.     

The effects of aluminum loading on selected tissue calcium and magnesium concentrations in rats

Biological Trace Element Research - Considerable evidence implicates elevated brain aluminum (Al) concentration in the pathogenesis of several forms of central nervous system dysfunction seen...     

Influence of magnesium deficiency on the bioavailability and tissue distribution of iron in the rat

We investigated the effect of dietary magnesium (Mg) deficiency on the nutritive utilization and tissue distribution of iron (Fe). Wistar rats were fed an Mg-deficient diet (56 mg/kg) for 70 days. Absorbed Fe, Fe balance, number of the erythrocytes [red blood cells (RBC)] and leukocytes white blood cells (WBC)], hemoglobin (Hb), and Fe content were determined in samples of plasma, whole blood, skeletal muscle, heart, kidney, liver, spleen, femoral bone, and sternum obtained on experimental days 21, 35, and 70. The Mg-deficient diet significantly increased Fe absorption and Fe balance from week 5 until the end of the experimental period. This effect was accompanied by a significant decrease in the concentration of RBC and Hb from day 35, which caused the decrease in whole blood Fe seen on day 70. However, WBC were significantly increased from day 21 until the end of the experimental period. Mg deficiency significantly increased plasma and liver Fe at all three time points investigated. Spleen, heart, and kidney Fe were significantly increased only at the end of the study. However, on day 70, Fe concentration in the sternum had decreased significantly. No changes were found in skeletal muscle or femur Fe content. Mg deficiency led to increased intestinal absorption of Fe and decreased RBC counts, possibly as a result of increased fragility of the erythrocytes. Intestinal interactions between Fe and Mg, together with activation of erythropoiesis as a result of hemolysis, favored intestinal absorption of Fe. This situation gave rise to an increase in plasma Fe levels, which in turn favored Fe uptake and storage by different organs, especially the liver and spleen. However, despite the increased Fe content seen in the tissues of rats fed the Mg-deficient diet, these animals were unable to compensate for the hemolysis caused by this nutritional deficiency.     

Effect of selenium and vitamin E supplementation on lipid abnormalities in plasma, aorta, and adipose tissue of Zucker rats

Twenty-nine obese female Zucker rats (fa / fa) were fed with a laboratory chow supplemented or not with a selenium-rich yeast (Selenion), or Selenion + vitamin E, or vitamin E alone. Twelve lean female Zucker rats (Fa / Fa) of the same littermates fed with the same diet were used as control. After 32 wk of diet, obesity induced a large increase in plasma insulin and lipid levels. A significant decrease in the plasma vitamin E/triglycerides ratio (p < 0.005) and an increase in plasma thiobarbituric reactive substances (TBARS) (p < 0.005) were also observed. Plasma selenium and vitamin E increased in all supplemented rats. The plasma insulin level was decreased by selenion supplementation and the vitamin E/triglycerides ratio was completely corrected by double supplementation with Selenion + vitamin E. TBARS were also efficiently decreased in two obese groups receiving vitamin E. In plasma, adipose tissue and aorta, obesity induced an increase in palmitic acid (C16:0), a very large increase in monounsaturated fatty acids (palmitoleic acid C16:l, stearic acid C18:l) associated with a decrease in polyunsaturated n-6 fatty acids (linoleic acid C18:2 n - 6, arachidonic C20:4 n - 6). These alterations in fatty acid distribution were only partly modulated by Se and vitamin E supplements. However, in the aorta, antioxidant treatment in obese rats significantly reduced the increase in C16:0 and C16:l (p < 0.05 andp < 0.01, respectively) and the decrease in arachidonic acid (p < 0.05). These changes could be beneficial in the reduction of insulin resistance and help to protect the vascular endothelium.