Concentrations of essential elements after repeated administrations of tin and selenium

To study effects of simultaneous administration of tin (Sn) and selenium (Se) on concentrations of several essential elements, mice were injected with either SnCl2 (ip) or Na2SeO3 (sc), alone or both compounds at a daily dose of 5 mumol/kg each for 12 consecutive days. Mice were sacrificed at 20 h after the last injection and concentrations of Sn, Se, Na, Ca, Zn, P, Fe, K, and Mg in the liver, kidney, spleen, pancreas, testis, seminal vesicle, lung, femoral muscle, and femoral bone were determined. In the control mice, Sn and Se concentrations were the highest in bone (0.69 micrograms Sn and 6.93 micrograms Se/g dry wt). Administered Sn was found to accumulate in all organs except the testis. Among the essential elements determined, Na was the most affected in terms of concentration in the organs and Mg was the least affected element in these organs. Among the organs tested, each elemental concentration in the pancreas was most affected. Simultaneous injections of Sn and Se appeared to keep the correlation coefficients between elements similar to those found in the control mice.     

Dietary calcium and blood lead levels in women

Nutritional factors are known to influence metabolism and toxicity of several metals in animal experiments, but relevant human data are scarce and inconclusive. In this work, we tested the hypothesis that dietary calcium influences lead metabolism in humans. Blood lead concentrations were used as indicators of lead exposure and metabolism. Two groups of peasant women living in similar conditions in two different regions in Yugoslavia (100 in each) were chosen as subjects for this purpose. In region A, the dietary calcium intake was about 940 mg, and in region B about two times lower, i.e., 450 mg/day. The average blood lead concentration was significantly lower in women from region A (69 micrograms/L) than from region B (83 micrograms/L). Our results support the assumption that adequate calcium intake might be one of the preventive measures for decreasing lead absorption. This new evidence, sought for some time by nutritionists and toxicologists, needs further international confirmation.     

Mercury and selenium distribution in human kidney cortex

Concentration of mercury and selenium were analyzed in tissue fractions of human kidney cortex samples from seven autopsy cases. Total mercury content ranged between 0.3–9.0 nmol Hg/g wet wt. Between 27–61% of the total mercury was found in the 105,000g supernatant of the tissue homogenate from six cases. In kidney cortex from the seventh case, a deceased dentist with the highest concentration of mercury, only 3% of the total mercury was found in the 105,000g supernatant and about 88% in a SDS-insoluble fraction. In this fraction the molar ratio between mercury and selenium was close to 1∶1. This study supports results from previous animal studies and indicates that mercury in human kidney cortex could be deposited in forms with different solubility. It could be of importance to speciate different forms of mercury in tissues according to solubility and association to selenium when interpretations of mercury concentrations are made.     

Zinc protection against cadmium effect on estrual cycle of wistar rat

A single dose of cadmium chloride (2.2 mg/kg of body wt) increased the estrual cycle period about two times. This effect could be prevented by means of simultaneous administration of zinc at the same dose.     

The distribution of cadmium within the human prostate

Five normal prostates from autopsies of humans aged 61-76 yr were divided into 2 x 24 topographically well-defined pairs of slices that were analyzed for cadmium (Cd) and examined histologically. The corresponding kidney cortex concentrations were also determined. The concentrations in ng Cd/g wet wt were in the range of 50-500 in the prostates and 8,000-39,000 in the kidneys with good mutual correlation. Large variations in Cd concentrations within the prostates were found. The concentrations were highest at the base (near the bladder) and lowest at the apex of the gland. Furthermore, large variations within horizontal layers were found, and this variation was not correlated to the histological amount of stroma or glands.     

Metabolic deposition of selenium and cadmium into the hair and other tissues of the guinea pig

To better understand the significance of hair trace-element measurements and their relationships with the trace-element levels in body organs and fluids, a series of controlled animal experiments were conducted in which several trace elements were periodically measured during a 90-day chronic exposure to selenium and cadmium. Chronic selenium exposure appeared to be reflected by elevated selenium levels in the hair, kidneys, and liver. Chronic cadmium exposure, although reflected by kidney and liver elevation, appeared not to be reflected by corresponding increases in its concentration in the hair.     

Maternal hair zinc concentration in neural tube defects in Turkey

Hair zinc concentration was measured in samples taken from 57 mothers who delivered infants with neural tube defects (NTD) (mainly anencephaly). Control groups consisted of 30 healthy mothers with normal offspring and 37 nonpregnant women from middle-income backgrounds. Zinc concentration was also measured in the hair of eight infants with NTD (four being anencephalic). The mean maternal hair zinc concentration in the NTD group (128.2 +/- 38.9 micrograms/g) was lower than that of the control women (p less than 0.001), whereas the mean hair zinc level of malformed babies (250.4 +/- 85.2 micrograms/g) was significantly higher than that of normal infants (193.4 +/- 39.2 micrograms/g) (p less than 0.05). Maternal nutritional zinc deficiency was thought to be one of the factors responsible for NTD in Turkey.     

The effects of cadmium on zinc absorption in isolated rat intestinal preparations

The effect of cadmium on zinc absorption was studied using an isolated vascularly and luminally perfused rat intestinal preparation.⁶⁵Zn as well as Zn and Cd (both as the chloride salt) were added to the luminal perfusion medium (LPM) at varying concentrations. Over a 90-min period, the amount of Zn appearing in the vascular perfusion medium (VPM) and that retained by the tissue post-perfusion was estimated. Cd at all levels studied (0.03, 0.10, 1.0, and 10.0 μg/mL) reduced the amount of Zn appearing in the VPM in comparison with control perfusions (no detectable Cd in the LPM) when the initial Zn concentration was 5 μg/mL. Similarly, with an initial Zn concentration of 10 or 20 μg/mL, the amount of Zn appearing in the VPM was reduced when the Cd concentration was 0.1 or 1.0 μg/mL. With these same Zn concentrations, the amount of Zn retained by the tissue was higher when the Cd concentration was 10 μg/mL. These results demonstrate that Cd at low concentrations is capable of reducing Zn appearance in the VPM.     

Determination of selenium in duplicate diets of residents of Pinhel,Portugal, by neutron activation

A rapid cyclic instrumental neutron activation analysis (CINAA) method has been used to determine the selenium content of 27 duplicate diet samples from each of the 27 districts surrounding Pinhel, Portugal. The accuracy and precision of the CINAA method have been evaluated by analyzing certified reference materials and observed to be within ±5–10% for samples containing at least 40 ppb of selenium. The detection limit has been found to vary between 26–42 ppb selenium depending on the sample composition. The average daily dietary intake has been calculated as 37 μg of selenium per day.     

Oral and subcutaneous administration of cadmium chloride and the distribution of metallothionein and cadmium along the villus-crypt axis in rat jejunum

The route of Cd uptake influences the distribution of Cd, other metals, and metallothionein (MT). Although intestinal MT levels related to the tissue mass did not show proximodistal gradients after sc administration of CdCl₂, orally administered high doses of CdCl₂ increased mucosal MT levels longitudinally from the duodenum to the ileum. The gradient abolished when the mucosal MT level was related to the intestinal length. To further elucidate this finding, three groups of rats were studied: a control group, a group receiving dietary CdCl₂, and a group receiving sc injections of CdCl₂. The small intestine was removed after a 14-d treatment. Midjejunal segments were mounted in a cryomicrotome and cut transversally into five layers along the villus-crypt axis. Mucosal enzymes were measured to control these sections. Cd was measured by AAS and MT by RIA. Alkaline phosphatase and lactase activities exhibited the typical villus-crypt gradient. Mucosal MT levels paralleled those of Cd. Although Cd and MT concentrations were high at the tip of the villi and low in the crypts after oral administration, sc treatment reversed that profile. A molar Cd-MT ratio of approx 10 or 1 was reached after po or sc treatment, respectively. This demonstrates that only oral Cd may lead to an accumulation of Cd in the mucosal tissue fairly exceeding the binding capacity of small intestinal MT. The results show that different routes of Cd intake lead to a different MT-induction pattern in the intestinal wall and that longitudinal Cd and MT concentration gradients in the small intestine observed after high oral doses are a result of their high levels at the villus tips.     

Enhancement of the kidney Cd burden by SH-containing chelating agents

The accumulation of Cd in the kidneys is enhanced markedly if chelating agents that contain SH-groups like 2,3 dimercaptopropanol (BAL) are injected immediately after the metal. This is not a transient effect but persists for more than 3 d. It is less pronounced at higher chelate doses or when the pH of urine is increased. Our experiments indicate that chelating agents, which form unstable complexes at acid pH and are able to pass through the cell membrane, will cause metal accumulation in the kidneys.     

The effect of diabetes on the molecular localization of maternal and fetal zinc and copper metalloprotein in the rat

The molecular localization of maternal and fetal zinc and copper metalloproteins in diabetic and control rats was studied. Compared to controls, liver and kidneys of diabetic dams showed an increased concentration of zinc and copper that was associated with metallothionein. In contrast, fetuses of diabetic dams had lower zinc and metallothionein levels than fetuses from controls. The abnormal maternal trace element metabolism seen with diabetes resulted in alterations of zinc uptake and/or retention of their fetuses.     

Iron,copper, and zinc status in rats fed supplemental nickel

Literature data concerning the effect of increasing dietary Ni concentrations on Fe, Cu, and Zn status in rats are sparse and, in part, controversial. Therefore, the effects of the addition of either 0, 3, 50, or 100 mg Ni/kg diet on Fe, Cu, and Zn status of rats were investigated in two separate experiments. Purified diets were used that were composed according to the established nutrient requirements of rats. Ni in kidney was increased with increasing Ni intakes. Dietary Ni did not significantly influence Fe concentrations in plasma, liver, kidney, femur, and spleen. Likewise, the addition of Ni to the diet did not alter Cu status. Zn concentrations in femur were significantly decreased after feeding the diets with 100 mg Ni/kg. However, Zn in plasma, liver, kidney, and spleen was not affected. It is concluded that variations in dietary Ni concentrations have no major impact on Fe, Cu, and Zn status in rats.     

Copper and zinc in experimental hypertension

The role of the trace minerals, copper (Cu) and zinc (Zn) are important in maintaining blood pressure. Copper has been found to inhibit the activity of angiotensin's converting enzyme. An interrelationship has been found to exist between Cu and Zn. Data in renal (RH) and spontaneous hypertensive rates (SHR) regarding Cu and Zn is lacking. The purpose of this report was to measure Cu and Zn levels in two types of experimental animal models of hypertension compared to normotensive (NT) rats. Blood samples were drawn to measure serum levels of Cu and Zn in three types of animals, RH, SHR, and NT. Serum Cu values were found to be lower, whereas Zn levels were elevated in the SHR animals. Serum levels of Cu and Zn in the RH animals were similar to those found in the NT animals. Further study of the interaction of those trace minerals is documented, and extends over knowledge of the role of minerals in blood pressure control.     

Decreased thiamine and magnesium levels in the potentiation of the neurotoxicity of lead in occupational lead exposure

The relationship between blood lead (Pb) and serum levels of calcium and of neural nutrients such as thiamine and magnesium (Mg) has been determined in a Nigerian population that is occupationally exposed to Pb. Forty-seven male Pb workers were recruited as test subjects and 25 males unexposed to Pb served as controls. The test subjects were classified into three groups, based on severity of exposure to Pb. Blood lead (BPb) and the serum levels of Mg, thiamine, and calcium were determined in both test subjects and controls. The mean blood Pb level was not significantly higher in Pb workers. In contrast, Mg and thiamine levels were significantly decreased (p<0.05; p<0.01, respectively). However, the calcium level was not significantly lower in test subjects than in controls. Also, there was a significant negative correlation between serum thiamine and blood Pb levels (r=-0.50; p<0.01). Furthermore, there was a significant negative correlation between serum calcium and BPb levels (r=-0.41; p<0.01). This study has shown that relatively low BPb levels can enhance Pb absorption and also potentiate Pb neurotoxicity in the presence of decreased serum thiamine and Mg levels.     

Effects of low copper and high zinc intakes and related changes in Cu,Zn-superoxide dismutase activity on DMBA-induced mammary tumorigenesis

The effect of low copper and high zinc intakes on Cu,Zn-superoxide dismutase (Cu,Zn-SOD) activity and mammary tumorigenesis induced by 9,10-dimethyl-1,2-benzanthracene (DMBA) was investigated. Groups of 40 weanling female Sprague-Dawley rats were fed a modified AIN-76 diet containing the following (/kg diet): 1 mg Cu (0.016 mmol) and 30 mg Zn (0.459 mmol); 6 mg Cu (0.094 mmol) and 30 mg Zn (0.459 mmol) (control); or 6 mg Cu (0.094 mmol) and 150 mg Zn (2.295 mmol) for 21 wk. At 5 wk, 30 rats/group were given 4 mg (15.6 mumol) DMBA in corn oil intragastrically, and controls (10/group) received corn oil alone. Erythrocyte Cu,Zn-SOD activity was measured at 3, 5 (just before DMBA), 9, 13, 17, and 21 wk. The group fed the high-Zn diet had a slightly lower weight gain and food consumption. DMBA treatment had no effect on these parameters. Plasma and liver Cu concentration decreased in the low-Cu group. Femur zinc was significantly elevated in the high-Zn group. Erythrocyte Cu,Zn-SOD activity was decreased in the low-Cu group from 3 to 21 wk and was significantly elevated in the high-Zn group at 3 and 5 wk. In the low-Cu group, there were 5 nonmalignant adenomas and 3 malignant adenocarcinomas; in the control group, there were 4 adenomas and 3 adenocarcinomas; in the high-Zn group, there were 5 adenomas and 3 adenocarcinomas. No relationship between Cu,Zn-SOD activity and the presence of tumors could be found.     

The responses of hepatic monooxygenases of guinea pig to cadmium and nickel

When Cd (3.58 mg CdCl₂·H₂O/kg, ip) was administered to male guinea pigs 72 h prior to sacrifice, the metal significantly inhibited the aniline 4-hydroxylase (AH) (16%), ethylmorphoneN-demethylase (EMND) (26%), and aminopyrineN-demethylase (AMND) (18%) activities and cytochrome P-450 (12%) and cytochrome b₅ (10%) levels. Cd did not alter the hepatic microsomal heme level. Cd, however, significantly increased the hepatic microsomalp-nitroanisoleO-demethylase (p-NAOD) (53%) activity. When Ni (59.5 mg NiCl₂·6H₂O/kg, sc) was administered to the guinea pigs 16 h prior to sacrifice, the metal significantly depressed AH (49%),p-NAOD (66%), EMND (47%), and AMND (37%) activities, and cytochrome P-450 (15%), cytochrome b₅ (24%), and microsomal heme (28%) levels. For the combined treatment, animals received the single dose of Ni 56 h after the single dose of Cd and then were killed 16 h later. In these animals, significant inhibitions were noted in AH (51%), EMND (47%), and AMND (30%) activities, and cytochrome P-450 (15%), cytochrome b₅ (26%), and microsomal heme (30%) compared to those of controls. In the case ofp-NAOD activity, the influence was in favor of Ni, i.e, the inhibition was about 61% by the combined treatment. These results reveal that:

Blood lead level distribution by age group in inhabitants of Ankara

Blood lead levels of 619 healthy and nonoccupationally exposed inhabitants of central and rural parts of Ankara, (297 females and 322 males) ages 2–80, were determined using atomic absorption spectrophotometry. Lead also was determined in the whole blood samples from 66 (all male) occupationally exposed adults. The blood lead levels were significantly higher (p<0.05) among children (16.95 μg/100 mL as a geometric mean) than the subdivided age groups of adults (geometric means by decades of age group were ranged from 8.39 μg/100 mL to 14.34 μg/100mL). The levels were lower among young adults and gradually to reach a plateau at the 50–59 age group. Although females had lower lead blood levels than males, sex difference was insignificant (p>0.05).     

Temporal changes in tissue glutathione in response to chemical form,dose, and duration of selenium treatment

Selenium has been reported to affect glutathione (GSH) concentrations in short-term animal-feeding experiments. Given the central role that this tripeptide plays in maintaining cellular homeostasis, it was hypothesized that perturbations in glutathione metabolism induced by selenium might account for its cancer chemopreventive activity. In the present study, four experiments were conducted in which the effect of acute, short-, or long-term exposure to selenium was assessed. Selenium was provided as either sodium selenite or D,L-selenomethionine. Selenite was observed to induce a biphasic response in total liver GSH. Injected selenium caused an acute reduction in GSH, whereas short-term feeding (up to 8 wk) increased both total GSH and oxidized glutathione (GSSH), an effect that gradually diminished in magnitude with prolonged feeding. Our data suggest that such changes are unlikely to account for the chemopreventive activity of selenium for the following reasons: Perturbations in glutathione metabolism occurred only at doses of selenite that approached toxicity. These doses are higher than what would be required for producing cancer chemoprevention. The transient nature of these changes also contrasts with the need for a continuous supplementation of selenite in suppression of tumorigenesis. Furthermore, selenomethionine was found to have little activity in altering glutathione metabolism, even though it compares favorably with selenite as a cancer chemopreventive agent. Nonetheless, these findings do not discount the possibility that sulfhydryl compounds, such as glutathione, might be used to modify the toxicity and/or enhance the cancer prophylactic activity of selenium compounds.     

Inhibition of copper absorption by zinc

Copper and zinc interact at the intestinal mucosal level, affecting copper absorption. Amino acids, such as histidine, may affect the absorption of these two elements by chelating these cations. The two mechanisms could have additive potential. This possibility was investigated using a duodenal-jejunal single-pass perfusion procedure in anesthetized rats. Copper absorption and tissue retention from solutions containing 0.1 mM copper were determined in the presence of either no zinc or equimolar zinc, or at a zinc/copper ratio of 10/1, either without histidine or with histidine at a 10/1 or 20/1 ratio to copper. Copper removal from the intestinal lumen was decreased by zinc, and further reduced by increasing concentrations of histidine. There was a greater accumulation of copper in the small intestine, reaching a maximum with a 10-fold excess of histidine. With zinc at a 10/1 ratio to copper, the addition of a 10- or 20-fold molar excess of histidine further decreased the net uptake of copper from the perfusate while greater copper accumulation in the tissue occurred. Histidine thus enhances the inhibitory effects of zinc on copper absorp|tion, suggesting the application of convergent mechanisms for diminishing copper uptake. This could be relevant for the treatment of Wilson’s disease.