Zinc Metabolism In Rat Research Articles

Disruption of the zinc metabolism in rat fœtal brain after prenatal exposure to cadmium

This study was carried out to investigate the effects of maternal Cd and/or Zn exposure on some parameters of Zn metabolism in fetal brain of Wistar rats. Thus, female controls and other exposed by the oral route during the gestation period to Cd (50 mg CdCl2/L) and/or Zn (ZnCl2 60 mg/L) were used. The male fetuses at age 20 days of gestation (GD20) were sacrificed and their brains were taken for histological, chemical and molecular analysis. Zn depletion was observed in the brains of fetuses issued from mothers exposed to Cd. Histological analysis showed that Cd exposure induces pyknosis in cortical region and CA1 region of the hippocampus compared to controls. Under Cd exposure, we noted an overexpression of the genes coding for membrane transporter involved in the intracellular incorporation of Zn (ZIP6) associated with inhibition of that encoding the transporters involved in the output of the Zn into the extracellular medium (ZnT1 and ZnT3). A decrease in the expression of the gene encoding the neuro-trophic factor (BDNF) associated with overexpression of the encoding the metal regulatory transcription factor 1 (MTF1), factor involved in the homeostasis of Zn, was also noted in Cd group. Interestingly, Zn supply provided a total or partial restauration of the changes induced by the Cd exposure. The depletion of brain Zn contents as well as the modification of the profile of expression of genes encoding membrane Zn transporters, suggest that the toxicity of Cd observed in fetal brain level are mediated, in part, by impairment of Zn metabolism.

Psychological Stress-Induced Lower Serum Zinc and Zinc Redistribution in Rats

In humans, long-term exposure to uncontrollable and unpredictable life stressors is a major precipitant in the development of depressive disorders. There are strong evidences that depression is accompanied by lower serum zinc. The aim of present study is to assess the effects of repeated psychological stress (PS) on the zinc metabolism in rat. The rats were divided into control group and PS group which were subdivided into three subgroups: 7-day group, 14-day group, and recovery group (ten rats in each subgroup). PS model was created by a communication box which contains room A and room B. Rats in room A were only exposed to the responses of rats which were randomly given electrical shock for 30 min in room B. PS was given to rats for 30 min every morning for 14 days. The serum corticosterone (CORT), zinc in serum and tissues, and zinc apparent absorption after PS exposure were investigated. The results showed that the serum CORT increased and serum zinc decreased after 7 and 14 days of PS treatment. The zinc concentration in the liver was increased by 14 days PS exposure, whereas its concentration in the hippocampus was decreased by 7 and 14 days of PS exposure. There were no significant changes in zinc concentration in the heart, spleen, kidney, duodenum, cortex, and cerebellum. A decrease in the zinc apparent absorption was observed in the 7- and 14-day PS groups. The increased serum CORT and liver zinc concentrations and decreased serum zinc and apparent absorption of zinc recovered to normal concentrations 7 days away from PS exposure. The results suggest that PS could induce lower serum zinc, which might be correlated with decreased zinc absorption in the small intestine and increased liver zinc accumulation after PS exposure. The consequent effects of decreased hippocampal and serum zinc and increased CORT concentration after PS exposure on stress-related diseases await further research.

Induction of metallothionein by exposure to normobaric 100% oxygen atmosphere in rats with different zinc supply

The objective of this study was to determine the effects of an oxygen enriched environment on the induction of the metalloprotein metallothionein (MT) and its relation to zinc metabolism in rats supplied with different levels of dietary zinc. Male albino rats were fed purified diets based on maize starch, egg white, saccharose and soybean oil differing in the concentration of zinc (1; 20; 100; 500 mg Zn/kg diet). At a dietary zinc supply of 1 mg/kg, the rats developed a zinc deficiency indicated by visual and biochemical parameters. At the end of the 37-day feeding period, half of the rats were exposed to 100% oxygen for 12 h.The oxygen treatment significantly reduced plasma zinc in the zinc supplemented rats and reduced it in tendency in the zinc deficient rats. The MT concentration was increased in the zinc supplemented groups in the liver, kidney and lung. The oxygen treatment elevated the metallothionein concentration in the two high zinc supplemented groups (100 and 500 mg Zn/kg diet) in the liver. The response of the zinc concentration in plasma and of hepatic metallothionein levels to oxygen exposure indicates a role of metallothionein in zinc distribution or interactions with other trace elements to support antioxidant capacity, rather than an impact on direct scavenging activity of free radicals.

Zinc metabolism in rats: Effects of intestinal resection, cholecalciferol and ascorbic acid

The metabolic balance technique was used to study the effect of dietary composition on zinc nutritive utilization in rats in which 50% of the distal small intestine (DSI) was removed, and in transected rats (controls). Six experiments with three different diets were done: the basal diet contained 12% protein (casein+5% D,L-methionine) and 4% lipid (medium chain triglycerides (MCT), olive oil and sunflower oil in equal parts); the other two diets were obtained by supplementing the basal diet with cholecalciferol (0.4 mg/kg diet) or adding ascorbic acid (150 mg/kg diet). Resection of 50% of the DSI markedly affected the digestive and metabolic utilization of zinc [apparent digestibility coefficient (ADC), and zinc balance] in rats fed on the basal diet alone or additioned with vitamin C. However, these parameters were not so markedly affected by the surgery in rats whose diet was supplemented with cholecalciferol. To investigate postresection zinc homeostasis we also measured the concentrations of this metal in blood, plasma and several organs (liver, femur, sternum, longissimus dorsi (LD) muscle and testes) one month after surgery. We found no alterations in the distribution of zinc in the organism under any of the experimental conditions. We conclude that the adaptive mechanisms that maintaining trace metal homeostasis are operative one month after intestinal resection.

Influence of butter and of corn, coconut and fish oils on the effects of recombinant human tumour necrosis factor-alpha in rats.

1. Tumour necrosis factor-alpha is produced in response to inflammatory stimuli. Fish oil can suppress the production and actions of cytokines. Little information is available on the effects of other fats on cytokine biology. We compared the effects of fats, with a wide range of fatty acid characteristics, on the effects of tumour necrosis factor-alpha on protein and zinc metabolism in rats. 2. Weanling rats were fed for 8 weeks on diets containing 10% fat in the form of corn, fish or coconut oils or butter before an intraperitoneal injection of recombinant human tumour necrosis factor-alpha was given. Measurements were made 24h after the injection. 3. In rats fed corn oil, food intake was reduced by 62% and rates of protein synthesis were increased by 86, 32 and 39% in the liver, lung and kidney, respectively. Zinc concentrations increased by 23% in the liver but decreased by 10% in the kidney. Plasma caeruloplasmin and complement C3 levels increased by 25% and 28%, respectively, and plasma albumin level decreased by 24%. 4. Fish oil prevented the increase in hepatic protein synthesis and changed the response of protein synthesis in lung and kidney to a decrease. Changes in hepatic and renal zinc concentrations were prevented. The response of the plasma caeruloplasmin level was unaltered but those of the plasma complement C3 and albumin concentrations were prevented. 5. Coconut oil and butter, although similarly low in linoleic acid, differed in their modulatory effects. With the exception of the rise in the plasma complement C3 concentration, all responses were prevented or greatly inhibited in rats fed butter.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of prednisone on growth and zinc metabolism in rats

Growth failure and increased susceptibility to infection are common complications of prednisone administration, which may be associated with reduced zinc nutriture. To test the hypothesis that prednisone administration interferes with zinc metabolism and impairs growth, 41 male, weanling Charles River rats weighing 43–60 g were randomly assigned to four groups. Three groups of 12 rats received prednisone daily for five weeks at dosages of 0.5, 2.0 and 8.0 mg/kg body weight per day, respectively. A fourth group receiving the maximum dose of prednisone. In the fifth week, all the animals received 65Zn at 0.5 uCi/100 g body weight by stomach tube. The retention of radioactivity was measured in a small animal whole body gamma counter. The results show that the rate of weight gain decreased in the prednisone-treated animals. In addition, while there were no significant differences in food intake between the three groups of prednisone-treated rats, the food efficiency ratio of 0.10±0.03 of the maximally-treated group was significantly lower (P<.001) than that of the pair-fed controls at 0.36±0.03 as well as those at the lower levels of prednisone treatment (with values between 0.25 to 0.29). The whole body 65Zn retention in the pair-fed control animals at 24 and 216 hours was greater than 90% and 60%, respectively, as compared with the retention of 60% and 10% at 24 and 216 hours in the rats administered the highest dose (8 mg/kg/day). Prednisone treatment depressed the capacity of the liver, kidney, muscle, bone and testes to accumulate 65Zn. Urinary excretion of zinc and nitrogen increased in proportion to the doses of prednisone used. We conclude that using growing rats, prednisone treatment impaired body weight gain and reduced food efficiency. At a high dosage the steroid decreased whole body 65Zn retention and increased the relative dry liver weight.