The effect of L-ascorbic acid and/or tocopherol supplementation on electrophysiological parameters of the colon of rats chronically exposed to lead

Background

The aim of this study was to assess the effect of diet supplementation with L-ascorbic acid (500 mg/L), tocopherol (3 mg/kg b.w.), and/or a water soluble analog of tocopherol (Trolox) (48 mg/L) on ion transport in the colon of rats subjected to a chronic exposure (9 months) to 0.1% lead acetate in drinking water.

Material/Methods

The electrophysiological parameters of the colon wall were measured with Ussing methods. Lead content in the whole blood was analyzed by graphite furnace atomic absorption spectrometry (GFAAS) using Zeeman correction. L-ascorbic acid and tocopherol in plasma was measured by high performance liquid chromatography. Immunohistochemical reaction was carried out for visualization of occludin, the intracellular tight junction protein.

Results

We showed a strong inhibitory effect of lead on the electrophysiological parameters, changes in intestinal permeability, disappearance of junctional occludin, decreased amount of mucus covering the colon surface, and the accumulation of PAS-positive substance in the apical region of the cytoplasm in the absorptive cells.

Conclusions

Supplementation with tocopherol or Trolox did not exert a beneficial influence on the studied parameters. L-ascorbic acid positively influenced the examined electrophysiological parameters, as it cancelled the inhibitory influence of lead on ion transport in the rat colon. L-ascorbic acid also protected against tight junction disruption of epithelial cells in the colon of the lead-treated rats. A similar effect was observed in the group of rats receiving lead and supplemented with L-ascorbic acid plus Trolox.

Changes in the concentration of microelements in the teeth of rats in the final stage of type 1 diabetes, with an absolute lack of insulin

The mineral content of tooth hard tissue may influence the rate of decay change. Considering this fact, we aimed at examining if type 1 diabetes might be a contributing factor to the appearance of tooth decay. The experiment was conducted on female Wistar rats. To induce diabetes, rats were intravenously injected with 1 mL streptozocine 0.01 M citrate buffer. The control group of rats was injected with 1 mL 0.01 M citrate buffer only. After 10 days, teeth and blood serum samples were obtained. Fluoride concentration was determined by potentiometer method, and calcium and magnesium, by AAS. Serum concentrations of glucose and estradiol in the diabetic rats were significantly higher compared to the control group. In the experimental group, a statistically significant decrease of fluorine concentration in both teeth and serum were observed. Calcium and magnesium concentrations in blood serum and dental magnesium concentration were significantly higher in rats with type 1 diabetes compared with the control. A downward trend in the content of dental calcium in streptozotocin-induced diabetic rats was observed. The results obtained indicate that caries initiation and progression could be promoted by metabolic changes associated with diabetes affecting the mineral composition of tooth hard tissue.

Changes in male reproductive system and mineral metabolism induced by soy isoflavones administered to rats from prenatal life until sexual maturity

OBJECTIVE

This study aimed to determine the influence of high-dose soy isoflavones (daidzein and genistein) administered from prenatal life to sexual maturity on testosterone and estradiol levels, testicular and epididymal morphology, the number of epididymal spermatozoa, and mineral metabolism in rats.

METHODS

Pregnant Wistar rats received orally soy isoflavones, daidzein, and genistein at a dose of 200 mg/kg of body weight per day. After separating sucklings from their mothers, male rats received the same dose of isoflavones until reaching the age of sexual maturity, i.e., for 3 mo.

RESULTS

In the isoflavone-treated group, statistically significant decreased concentrations of zinc (determined using atomic absorption spectrophotometry) in blood serum and increased concentrations in bone were observed. The isoflavones induced changes in the morphology of the seminiferous epithelium of rat testes. However, there were no significant changes in the number of spermatozoa in the epididymis. The levels of estradiol in serum and cauda epididymis homogenates of rats receiving phytoestrogens were significantly higher than in the control group. No differences were observed in testosterone concentrations in the serum of treated and control rats. The testosterone levels in the homogenates of the treated rat testes were significantly lower than in the control group.

CONCLUSION

The relatively mild effects of phytoestrogen administration on the morphology of testes and epididymides and the number of epididymal spermatozoa were observed despite the high dose used. The exposure of rats to genistein and daidzein during intrauterine life until sexual maturity influenced the mineral metabolism of the organism by significant decreases of Zn concentration in serum and increased Zn concentration in bones.

The content of selected chemical elements in the hair of young men of the Bantu language group from Tanzania versus environmental and social conditioning

Research works that would determine the content of chemical elements in black population organisms on the basis of hair analysis are not numerous. There are no studies referring to black populations living in indigenous environment, like the Mafinga region, Iringa District in Tanzania examined by us. The aim of the study performed was to analyse the content of chemical elements Fe, Ca, Mg, Zn and Cu in easily available biological media like hair. The material was collected in October 2005 and March 2006 during anthropological examination, which came from young males (n = 91), students of a secondary school. Large Ca concentration range was found for the total number of subjects (680.20 to 2,089.70 µg/g d.m.). Mean Fe content in hair for the total number of subjects was 11.19 ± 3.70 µg/g d.m., while that of Mg 6.84 ± 2.02 µg/g d.m. Mean Zn concentration for the total number of subjects was 91.06 ± 39.22 µg/g d.m., being significantly higher in younger group than in older one (p = 0.039). Mean Cu concentration in hair for the total number of subjects was 7.50 ± 2.90 µg/g d.m Body mass index (BMI = kg/m²) was calculated for the subjects showing that out of 91 men participating in the study 15.4% was characterised by mediocre nutrition. No statistically significant correlations were found between BMI and the analysed chemical elements. The analysis of the content of trace elements in the hair of the examined young males showed deficiencies in Zn, Cu, Fe and significantly in Mg.

Altered energy status of primary cerebellar granule neuronal cultures from rats exposed to lead in the pre- and neonatal period

This paper examines the effect of pre- and neonatal exposure of rats to lead (0.1% lead acetate in drinking water, resulting in rat offspring whole blood lead concentration (Pb-B) 4μg/dL) on the energy status of neuronal mitochondria by measuring changes in ATP, ADP, AMP, adenosine, TAN concentration, adenylate energy charge value (AEC) and mitochondrial membrane potential in primary cerebellar granule neurons (CGC) in dissociated cultures. Fluorescence studies were performed to imaging and evaluate mitochondria mass, mitochondrial membrane potential, intracellular and mitochondrial reactive oxygen species (ROS) production. The Na(+)/K(+) ATPase activity in intact CGC was measured spectrophotometrically. Our data shows that pre- and neonatal exposure of rats to Pb, even below the threshold of whole blood Pb value considered safe for people, affects the energy status of cultured primary cerebellar granule neurons through a decrease in ATP and TAN concentrations and AEC value, inhibition of Na(+)/K(+) ATPase, and increase in intracellular and mitochondrial ROS concentration. These observations suggest that even these low levels of Pb are likely to induce important alterations in neuronal function that could play a role in neurodegeneration.

Hymenolepis diminuta: the effects of infection on transepithelial ion transport and tight junctions in rat intestines

In this study, we examine the effect of Hymenolepis diminuta on ion transport in the ileum and on tight junctions in the ileum and colon of rats. We also evaluate the effect of H. diminuta on C-fiber endings in the ileum, the direct habitat of H. diminuta, before and after mechanical stimulation and pharmacological modification by capsaicin (C-fiber irritant). Wistar rats were orally infected with five cysticercoids of H. diminuta. Using a modified Ussing chamber, electrophysiological parameters of the ileum were measured (transepithelial electrical potential difference and transepithelial electrical resistance) as well as the deposition of occludin (a tight junction protein) in the ileum and colon of the rats 8, 16, 25, 35, 40 and 60 days post infection. We observed a significant reduction in transepithelial electrical potential difference in the ileum of rats infected with H. diminuta. In both the ileum and colon of rats infected with H. diminuta we also observed a decrease in occludin deposition, which indicates leakage of tight junctions, correlating with the decrease in transepithelial electrical resistance of these tissues. The application of capsaicin confirmed the hypothesis that H. diminuta in rats affects the C-fiber sensory receptors, causing changes in ion transport in the ileum. The results of the performed electrophysiological and immunohistochemical examinations indicate hymenolepidosis-related changes in the active transport of ions and the passive movement of ions.

Inhibition of erythrocyte phosphoribosyltransferases (APRT and HPRT) by Pb2+: a potential mechanism of lead toxicity

Many reports show that red blood cells of people exposed to lead have a decreased ATP concentration, decreased adenylate energy charge value and many metabolic and morphological abnormalities. Since the synthesis of nucleotides in erythrocytes occurs only through salvage pathways, we hypothesized that a decrease in nucleotide concentrations may be caused by lead-induced inhibition of erythrocyte phosphoribosyltransferases: adenine APRT (EC 2.4.2.7) and hypoxanthine-guanine HPRT (EC 2.4.2.8). These enzymes enable the reutilization of purine bases (adenine, guanine, hypoxanthine) converting them to mononucleotides (AMP, GMP, IMP), substrates for the synthesis of high-energy nucleotides. To confirm the hypothesis two experiments were performed: (i) in vitro, using a lysate of human erythrocytes incubated (5, 10, 30min) with lead ions (100microM, 10microM, 1microM, 500nM, 100nM lead acetate) and 100microM sodium acetate for the control, (ii) in vivo, using a lysate of rat erythrocytes taken from rats chronically exposed to lead (0.1% lead acetate in drinking water for 9 months, resulting in whole blood lead concentration 7microg/dL). The activities of APRT and HPRT were determined using HPLC method, which allowed concurrent determination of the activity of both enzymes in erythrocyte lysates. We have shown that, lead ions: (i) moderately inhibit both phosphoribosyltransferases in erythrocytes, this influence being detectable even at very low concentrations (ii) participate in hemolysis, the intensity of which negatively correlates with the activity of phosphoribosyltransferases. Our results indicate the necessity of further research on the role of lead-induced APRT and HPRT inhibition as one of the mechanisms of lead toxicity.

Elastin degradation within the abdominal aortic aneurysm wall--relationship between intramural pH and adjacent thrombus formation

BACKGROUND

The natural history of abdominal aortic aneurysm (AAA) is wall remodelling potentially leading to a final rupture. The pathogenesis of AAA appears to be multifactorial. The aim of this pilot prospective study was to assess the relationship between the thickness of the thrombus within the abdominal aortic aneurysm, intramural pH and local elastin degradation.

MATERIALS AND METHODS

The AAA size, intraluminal thrombus (ILT) morphology and location were evaluated in 206 consecutive patients. Thirty patients with large AAA (aortic diameter > or = 50 mm) and adjacent ILT with the thinnest part < or = 10 mm and thickest > or = 25 mm, measured in the region of the maximum diameter of AAA, were included for further study. During AAA surgery intramural pH measurements were performed and specimens taken from both thin thrombus-covered and thick thrombus-covered wall for computerized morphometric analysis.

RESULTS

Mean intramural pH value was 7.21 +/- 0.18 for the wall covered by thick ILT and 7.64 +/- 0.10 for the thin one (P < 0.001). Computerized morphometric analysis demonstrated that elastin fibres in the thin thrombus-covered wall were decreased in size (for width--P < 0.0001, for length--P < 0.13), irregularly orientated (P < 0.000001) and the amount of fibres was reduced when compared to the wall covered by thick ILT (P < 0.0004).

CONCLUSION

A strong relationship between intramural pH and elastin net destruction suggests that the local alkaline status within the thin thrombus-covered part of the aneurysm wall is contributing to the elastinolytic process.

Molecular determinants of Pb2+ interaction with NMDA receptor channels

Lead (Pb2+) is a potent neurotoxin that acts as a non-competitive, voltage-independent antagonist of the NMDA receptor (NR) channel. Pb2+ action partially overlaps with that of zinc (Zn2+), but precise coincidence with Zn2+ binding site is debated. We investigated the site of Pb2+ interaction in NR channels expressed in Xenopus laevis oocytes from the clones zeta1, epsilon1 or epsilon2 and mutated epsilon1 or epsilon2 forms. For each epsilon subunit we chose two mutations that have been identified as 'strong mutations' for Zn2+ binding and examined the effect of Pb2+ on channels that contained those mutations. In epsilon1-containing channels, mutations D102A and H128A caused a decrease of Pb2+ inhibition with a 10-fold (D102A) and four-fold (H128A) shift of IC50. In epsilon2-containing channels, the most effective mutation in removing Pb2+ inhibition was H127A, with a five-fold increase of IC50, while D101A was virtually ineffective. Other mutations, D104A, T103A, and T233A, were less effective. The double mutation D101AH127A, while reducing Zn2+ inhibition by nearly nine-fold, caused a minor (less than two-fold) shift in Pb2+ IC50. Competition experiments showed that increasing doses of Zn2+ reduced the apparent affinity for Pb2+ in epsilon1-containing receptors, but not in epsilon2-containing receptors. In addition the effect of Pb2+ on epsilon2-containing channels was additive with that of ifenprodil, with no competition for the site. Although none of the mutations that we have tested abolished the block by Pb2+, our results indicate that the action of this toxic metal on NR channels is more dependent on the receptor composition than previously thought, because Zn2+ is able to displace Pb2+ from its binding site in epsilon1-containing channels, but not in epsilon2-containing channels.

Increased Lipid Peroxidation and Ascorbic Acid Utilization in Testis and Epididymis of Rats Chronically Exposed to Lead

The hypothesis has been recently presented that lead may exert its negative effect at least partially through the increase of reactive oxygen species (ROS) level in tissues. However, little is known about the influence of lead intoxication on equilibrium between generation and elimination of ROS in the male reproductive system. Sexually mature male Wistar rats were given ad libitum 1% of aqueous solution of lead acetate (PbAc) for 9 months. Significantly higher lead concentrations were found in blood [median 7.03 (Q25-Q75: 2.99-7.65) versus 0.18 (0.12-0.99) microg dl-1, P < 0.01], caput epididymis [median 5.51 (Q25-Q75: 4.31-7.83) versus 0.51 (0.11-0.80) microg g-1 d.m., P < 0.001], cauda epididymis [median 5.88 (Q25-Q75: 4.06-8.37) versus 0.61 (0.2 - 1.08) microg g-1 d.m., P < 0.001] and testis [median 1.81 (Q25-Q75: 0.94-2.31) versus 0.17 (0.03-0.3) microg g-1 d.m., P < 0.01] of lead-intoxicated rats when compared to the control. The concentration of ascorbyl radical, generated in vitro from L: -ascorbic acid (present in tissues in vivo) was measured by means of Electron Paramagnetic Resonance (EPR) spectroscopy. The EPR signal of ascorbyl radical in caput epididymis, cauda epididymis, testis and liver of lead acetate-treated animals revealed a significant decrease by 53%, 45%, 40% and 69% versus control tissues, respectively. Plasma L: -ascorbic acid content measured by high performance liquid chromatography (HPLC) method and total antioxidant status (TAS) measured by means of spectrophotometry were also significantly lower in the intoxicated versus control animals (28% and 21%, respectively). In the group exposed to lead the concentration of lipid peroxide in homogenates of the reproductive system organs was significantly elevated versus control group. It can be assumed that the lower EPR signal was caused by decreased tissue concentrations of L: -ascorbic acid. The latter may have resulted from consumption of ascorbic acid for scavenging of ROS excess in tissues of animals chronically exposed to lead.

[Biochemical mechanisms of neurotoxic lead activity]

This article presents the latest study results on lead (Pb2+) neurotoxicity, in order to draw attention of the Polish public to the issue and initiate a nation-wide programme eliminating lead contamination effects, especially in children. We discuss the after-effect of exposure to lead in concentrations lower than presently accepted as 'safe'. The pathway of lead transport to the brain, and the effects of lead accumulation in neurons, oligodendroglia and astroglia, are examined. We also present the impairing influence of lead on the cognitive brain functions and learning abilities as a result of affecting three main neurotransmission systems: dopaminergic, cholinergic and glutaminergic. The present knowledge on the influence of lead on receptors, neutransmitter release and synaptic proteins.

The effect of new non-cross resistant antitumour agents on the energy state of human erythrocytes

Multidrug resistance (MDR) of tumour cells is related to the overexpression of ATP-dependent pumps responsible for the active efflux of antitumour agents out of resistant cells. Benzoperimidine and anthrapyridone compounds exhibit comparable cytotoxic activity against sensitive and MDR tumour cells. They diffuse extremely rapidly across the plasma membrane and render the ATP-dependent efflux inefficient. Such uptake could disturb an energy metabolism of normal cells possessing an elevated level of ATP-dependent proteins, especially erythrocytes having a high level of the MRP1, MRP4 and MRP5 proteins. In this study the effect of five antitumour agents: benzoperimidine (BP1), anthrapyridones (CO1, CO7) and reference drugs used in the clinic: doxorubicin (DOX) and pirarubicin (PIRA), on the energetic state in human erythrocytes has been examined. These compounds have various types of structure and kinetics of cellular uptake (slow--DOX, CO7, moderate--PIRA, fast--BP1, CO1) resulting in their different ability to saturate ATP-dependent transporters. The energetic state of erythrocytes was examined by determination of purine nucleotide contents (ATP, ADP, AMP), NAD(+) and values of adenylate energy charge (AEC) using an HPLC method. It was found that the level of nucleotides as well as the AEC value of erythrocytes were not changed during 24 h of incubation with these agents independently of their structure and ability to saturate ATP-dependent pumps. This is a very promising result in view of their potential use in the clinic as antitumour drugs against multidrug resistant cancers.

The purine nucleotide content in human leukemia cell lines

The HPLC method was used to determine the purine nucleotide (ATP, ADP, AMP, GTP, GDP, GMP, NAD(+)) contents and the values of the adenylate energy charge (AEC) and guanylate energy charge (GEC) for three human acute myelogenous leukemia (AML) cell lines: HL60 (M3 subtype of AML), THP1 (M5 subtype of AML), and HEL (M6 subtype of AML) in French-American-British classification (FAB) and for one chronic myelogenous leukemia (CML) cell line: K562. The results showed that the examined leukemic cells had some significant changes in their purine nucleotide concentrations relative to healthy cells. On the basis of the obtained results, it seems that two of the tested acute myelogenous leukemia cell lines, HL60 and HEL, have similar purine nucleotide metabolisms, while the third AML cell line, THP1, has a purine nucleotide metabolism like that of the chronic myelogenous leukemia cell line, K562.

The effect of new non-cross resistant antitumour agents on the energy state of human erythrocytes

Multidrug resistance (MDR) of tumour cells is related to the overexpression of ATP-dependent pumps responsible for the active efflux of antitumour agents out of resistant cells. Benzoperimidine and anthrapyridone compounds exhibit comparable cytotoxic activity against sensitive and MDR tumour cells. They diffuse extremely rapidly across the plasma membrane and render the ATP-dependent efflux inefficient. Such uptake could disturb an energy metabolism of normal cells possessing an elevated level of ATP-dependent proteins, especially erythrocytes having a high level of the MRP1, MRP4 and MRP5 proteins. In this study the effect of five antitumour agents: benzoperimidine (BP1), anthrapyridones (CO1, CO7) and reference drugs used in the clinic: doxorubicin (DOX) and pirarubicin (PIRA), on the energetic state in human erythrocytes has been examined. These compounds have various types of structure and kinetics of cellular uptake (slow--DOX, CO7, moderate--PIRA, fast--BP1, CO1) resulting in their different ability to saturate ATP-dependent transporters. The energetic state of erythrocytes was examined by determination of purine nucleotide contents (ATP, ADP, AMP), NAD(+) and values of adenylate energy charge (AEC) using an HPLC method. It was found that the level of nucleotides as well as the AEC value of erythrocytes were not changed during 24 h of incubation with these agents independently of their structure and ability to saturate ATP-dependent pumps. This is a very promising result in view of their potential use in the clinic as antitumour drugs against multidrug resistant cancers.

Effect of lead ions on rat erythrocyte purine content

The influence of short-term exposure to lead on the energetic status of erythrocytes in rats is reported in this study. The male Wistar rats selected for this study drank water containing 1% lead(II) acetate and/or intraperitoneal injections of 1 or 2 mg/kg body wt every 4 d starting on the eighth of the experiment, over a period of 1 mo. The whole-blood lead concentration measured after 4 wk was 1.51-35.31 microg/dL. The concentrations of adenosine, adenosine triphosphates, diphosphates, and monophosphates (ATP, ADP, and AMP), guanine triphosphates, diphosphates and monophosphates (GTP, GDP, and GMP), guanosine (Guo), inosine (Ino), inosine monophosphate (IMP), hypoxantine (Hyp), and nicotinamide dinucleotide and its phosphate (NAD(+) and NADP(+)) were determined by high-performance liquid chromatography (HPLC). The mean concentrations of ATP, GTP, NAD(+), and NADP(+) and those of adenylate (AEC) and guanylate (GEC) were significantly reduced in erythrocytes from the animals exposed to lead when compared to untreated controls. These results suggest that a lead ion disrupts the erythrocyte energy pathways. The decreases of NAD(+) and ATP could be used as an indicator of the extent of exposure to low levels of lead.

The effect of lead ions on the energy metabolism of human erythrocytes in vitro

The aim of this work was to evaluate the influence of chronic exposure to lead ions on the parameters of energetic status of human erythrocytes in vitro. Umbilical cord erythrocytes were incubated with lead acetate at final lead ion concentrations ranging from 10 to 200 microg/dl. ATP, ADP, AMP, adenosine, GTP, GDP, GMP, guanosine, IMP, inosine, hypoxanthine, NAD and NADP concentrations in erythrocytes were determined using HPLC. Scanning electron micrographs of erythrocytes were taken. The mean concentrations of ATP, GTP, NAD and NADP, and mean values of adenylate energy charge (AEC) and GEC in cells incubated at the presence of lead ions were significantly lower after 20 h of incubation. Concentrations of purine degradation products (Ado, Guo, Ino) and Hyp were significantly higher. It is suggested that lead ions affect the energy metabolism of erythrocytes. Morphological changes in erythrocytes correspond to the increase of lead ions in the incubation mixture and to the decrease of ATP concentration in erythrocytes. A decrease in NAD and ATP concentration in erythrocytes could be a sensitive indicator of energy process disturbance, useful in monitoring in case of chronic lead exposure.

[The impact of lead ions on metabolism of erythrocytes]

Lead contamination of the environment constitutes one of the major ecological problems. The determination of blood lead concentration is essential for evaluating lead exposure. Lead ions result in changes in the activity of numerous enzymes, disturb metabolic pathways of cells (inhibition of glycolysis), and inhibit synthesis of haem and globin. However, the activity of lead via pathological formation of free radicals is thought to be one of the most important molecular mechanisms of lead toxicity. Based on available literature, the issues concerning the effect of lead on metabolism of erythrocytes is discussed in this paper.