The effect of low lead doses in vitro and in vivo on the d-ala-d activity of erythrocytes, bone marrow cells, liver and brain of the mouse

The effects of hexachloronaphthalene on selected parameters of heme biosynthesis and systemic toxicity in female wistar rats after 90-day oral exposure

Hexachloronaphthalenes (HxCNs) are the most toxic congeners of polychlorinated naphthalenes, a group of compounds lately included into the list of persistent organic pollutants (POPs). This study presents the effects of 90-day intragastric administration of HxCN to female Wistar rats at doses of 0.03, 0.1, and 0.3 mg/kg body weight. The study examined selected parameters of the heme synthesis pathway, oxidative stress, hepatic cytochromes level, and basic hematology indicators. A micronucleus test was also performed. The subchronic exposure of rats to HxCN resulted in disruption of heme biosynthesis, hematological disturbances, and hepatotoxicity. The highest dose of HxCN inhibited aminolevulinic acid dehydratase (ALA-D) and uroporphyrinogen decarboxylase (URO-D). Accumulation of higher carboxylated porphyrins in the liver and increased excretion of 5-aminolevulinic acid in the urine was observed after a dose of 0.1 mg/kg body weight. The most sensitive effect of HxCN in rats was very strong induction of hepatic CYP1A1 activity, which was observed after the lowest dose. The highest dose of HxCN induced significant thrombocytopenia, thymic atrophy and hepatotoxicity, expressed as hepatomegaly and hepatic steatosis.

Octabromodiphenyl ether - porphyrogenicity after repeated administration to rats

OBJECTIVES

Octabromodiphenyl ether (OctaBDE) is a flame retardant which has been withdrawn from common use due to its negative effect on the environment. The literature data regarding its toxicity addresses its effect on liver function, the endocrine and reproductive systems, as well as its developmental toxicology aspects. The aim of this study was to investigate the effect of repeated administration of OctaBDE on heme biosynthesis in rats.

MATERIALS AND METHODS

The study was performed on female Wistar rats. OctaBDE was administered intragastrically at four different doses (2, 8, 40 or 200 mg/kg/day) for 7, 14, 21 or 28 days. The following measures of heme synthesis disturbance were used: urinary excretion of porphyrins, liver concentration of porphyrins, the activity of delta-aminolevulinate synthase (ALA-S) and delta-aminolevulinate dehydratase (ALA-D) in the liver.

RESULTS

After 28 days of exposure, lower ALA-S and ALA-D activity was observed in the liver. Additionally, increased concentrations of high carboxylated porphyrins (octa- and heptacarboxyporphyrins) were found in the liver: from 2- to 10-fold after the 2 mg/kg/day doses and from 4- to 14-fold after the 8-200 mg/kg/day doses. The porphyrogenic effect of OctaBDE was also evidenced by augmented, dose-dependent and exposure time-dependent, concentrations of total porphyrins in urine (2-7.5-fold increase) and their urinary excretion (2-9-fold increase). Tetracarboxyporphyrins predominated in the urine; their concentrations increased 2.5-10 fold.

CONCLUSIONS

The study revealed that repeated exposure to OctaBDE affects heme biosynthesis and the levels of porphyrins. The lowest effective level which induced changes in porphyrin concentration was 2 mg/kg/day.

Biochemical effects of lead exposure on systolic & diastolic blood pressure, heme biosynthesis and hematological parameters in automobile workers of north karnataka (India)

The purpose of this study was to find out the effect of lead exposure on systolic and diastolic blood pressure, heme biosynthesis related and hematological parameters of automobile workers. For this study 30 automobile workers were selected and compared with 30 age matched healthy control subjects. Significantly increased blood lead (364%, P < 0.001) and urinary lead (176%, P < 0.001) levels were observed in automobile workers (study group) as compared to controls. Systolic blood pressure (5.32%, P < 0.05) and diastolic blood pressure (5.87%, P < 0.05) were significantly increased in the automobile workers as compared to controls. The significantly decreased non-activated erythrocyte δ-aminolevulinic acid dehydratase (δ-ALAD) (-18.51%, P < 0.01) and activated δ-ALAD (-13.29%, P < 0.05) levels were observed in automobile workers as compared to normal healthy control subjects. But the ratio of activated/non-activated δ-ALAD was significantly increased (43.83%, P < 0.001) in automobile workers as compared to controls. Excretions of δ-aminolevulinic acid (83.78%, P < 0.001) and porphobilinogen (37%, P < 0.001) in urine were significantly increased in the study group as compared to the controls. In automobile workers heamoglobin (-11.51%, P < 0.001), hematocrit (-4.06%, P < 0.05), mean corpuscle volume (-3.34%, P < 0.05), mean corpuscle hemoglobin (-5.66%, P < 0.01), mean corpuscle hemoglobin concentration (-7.67%, P < 0.001), red blood cell count (-14.6%, P < 0.001) were significantly decreased and total white blood cell count (11.44%, P < 0.05) increased as compared to the controls. The results of this study clearly indicate that the absorption of lead is more in automobile workers and it affects on blood pressure, heme biosynthesis and hematological parameters observed in this study group.

Hepatotoxicity of monobromobenzene and hexabromobenzene: effects of repeated dosage in rats

The aim of the study was to determine whether monobromobenzene (BB) and hexabromobenzene (HBB) administered repeatedly (for 28 days) to female rats resulted in disturbances of heme synthesis. 5-Aminolevulinate dehydratase (ALA-D) and 5-aminolevulinate synthase (ALA-S) activities were slightly changed and the concentration of glutathione increased. The excretion of 5-aminolevulinic acid (ALA-U) in urine after all doses of BB and HBB increased already in the first week. After BB administration, increased excretion of coproporphyrins was detected only at the highest dose. The increased excretion of coproporphyrins following the administration of HBB could be observed already at the lowest dose (15 mg/kg). The excretion of uroporphyrins increased after two higher doses (75 and 375 mg/kg) in the fourth week of exposure. HBB also caused elevation of microsomal P450 level. The data suggest porphyrogenic activity of HBB; whereas in the case of BB we cannot exclude that elevated excretion of ALA-U resulted from kidney impairment.

The effect of aluminum chloride on some steps of heme biosynthesis in rats after oral exposure

Certain disturbances in heme biosynthesis induced by aluminum chloride were examined. The experiment was performed on female rats that received AlCl3 orally at the dose 100 mg Al/kg daily for 21 d. The effects of aluminum on the activity of delta-aminolevulinic acid synthetase (ALA-S), dehydratase (ALA-D), and heme oxygenase (O.H.) were observed on 3, 7, 14, and 21 d in liver and kidneys of rats. Also the activity of ALA-D in blood and the concentration of delta-aminolevulinic acid (ALA-U) in urine were observed. Orally administered aluminum caused increase in the activity of ALA-D in the liver and blood, and parallel decrease of ALA-U in urine (r = -0.85) of rats. Aluminum chloride also induced an increase of ALA-S and O.H. in the liver but not in the kidneys. The changes of the enzymes activity participating in heme biosynthesis after administration of aluminum may be correlated with anemia and iron metabolism in rats.

Effect of small doses of ethylene glycol monomethyl ether on the acetylcholinesterase and delta-aminolevulinic acid dehydratase activity in erythrocytes, blood and bone marrow of rats

The effect of small doses of ethylene glycol monomethyl ether (EGMME) on the activity of acetylcholinesterase (ACHE) in erythrocytes and whole blood as well as on the delta-aminolevulinic acid dehydratase (ALA-D) in blood and bone marrow was studied in Wistar rats. Significant reduction in the activity of both enzymes was noted three days after ip administration of 200 mg/kg b.w. EGMME whereas seven days later the activity of both enzymes returned to the control levels. Activity of ALA-D in blood appeared to be most sensitive to EGMME, and reacted even to the lowest dose, which did not significantly alter activity of ACHE or ALA-D in bone marrow. Haematological parameters in all treated groups remained unaltered.

Disturbances in heme biosynthesis in rabbits after administration per os of low doses of tin or lead

The experiment was performed on female rabbits that received per os equimolar doses (17 microM Me/kg) of SnCl2 x 2 H2O or Pb (CH3 COO)2 every day for 5 d. The activity of delta-aminolevulinic acid dehydratase (ALA-D) in the whole blood, liver, kidneys, brain, spleen, and bone marrow, concentration of free erythrocyte protoporphyrins (FEP), activity of delta-aminolevulinic acid synthetase (ALA-S) in the liver and bone marrow, urine delta-aminolevulinic acid (ALA-U), and coproporphyrins (CP-U) were determined. Lead and tin concentrations in the blood were estimated. Lead caused a significant inhibition of ALA-D in the blood, increased FEP concentration, and ALA and CP excretion in urine of rabbits. Lead also decreased ALA-D activity in the bone marrow and in the liver, and did not change ALA-S activity in the liver and bone marrow. Tin did not change any of the examined indices. Tin doses applied in the present study, maintained within the limits of permissible standards of metal levels in human diet, did not affect the process of heme biosynthesis in rabbits.

Combined exposure to lead and ethanol on tissue concentration of essential metals and some biochemical indices in rat

The effect of daily oral administration of ethanol (2.5, 5, or 10% in drinking water for 8 wk), lead (10 mg/kg, po, once daily for 8 wk), or their combination on tissue trace-metal concentration and hematopoietic and hepatic biochemical indices was investigated in male rats. Ethanol (10%) ingestion enhanced the hepatic lipid peroxidation and decreased the calcium and magnesium content of blood and liver. Coexposure to lead and ethanol (5 and 10%) produced a more pronounced elevation of blood zinc protoporphyrin (ZPP) and hepatic lipid peroxidation. Combined lead-ethanol exposure also lowered the concentration of blood and hepatic magnesium and calcium and increased the amount of lead in the blood, liver, and brain compared to a group treated with lead alone. The results suggest that chronic alcohol ingestion results in calcium and magnesium loss. However, coexposure to lead and ethanol could result in more serious depletion of calcium and magnesium, and this could be the cause of suspected synergism between alcohol consumption and lead poisoning.

Effect of acute lead intoxication on the ultrastructure of neutrophils in the peripheral blood of the rat

The influence of lead acetate on the ultrastructure of peripheral neutrophils was investigated in adult male rats. It was found that a single intraperitoneal administration of lead at dose 150 mg Pb/kg b.w. led to ultrastructural changes in the neutrophils at 3 and 6 h post injection. At the time of testing the exposed population had a mean (+/- SD) blood lead concentration from 206.2 +/- 24.8 micrograms/100 ml to 75.2 +/- 9.9 micrograms/100 ml compared with a mean value of 4.0 +/- 0.7 micrograms/100 ml for the control groups. The ultrastructural alterations such as irregular nuclei with deep invaginations, plasma membrane pockets, the presence of vacuoles with a heterogeneous material and an increasing amount of RER cisternae, were most clearly expressed 6 h after lead administration. In addition there appeared sometimes nuclear pockets, and a prominent crystalline inclusion placed in the cytoplasmic matrix of some neutrophils. No differences in the mitochondrial morphology and cytoplasmic granule pattern between exposed and control rats were observed.

Influence of metal chelators on metalloenzymes

The influence of chelating agents (1 mmol/kg/day X 6,i.p.) on trace metal mobilization and activities of certain metalloenzymes was investigated in rats. Calcium disodium ethylenediamine tetraacetate (CaNa2EDTA) and calcium trisodium diethylenetriamine pentaacetate (CaNa3DTPA) enhanced urinary excretion of Zn, while sodium 2,3-dimercaptopropane-1-sulfonate (NaDMPS) and sodium diethyldithiocarbamate (NaDDC) increased that of Cu. The activity of Zn-metalloenzymes-blood delta-aminolevulinic acid dehydratase (delta-ALA-D), plasma alkaline phosphatase (ALP) and that of Cu-metalloenzyme-plasma amine oxidase was decreased as a consequence of chelation therapy. However, hepatic levels of delta-ALA-D, ALP and alcohol dehydrogenase remained unaffected by chelation. The activity of hepatic Fe-metalloenzyme-catalase was increased by polyaminocarboxylic acids and lowered by thiol chelators. The metal chelators decreased the hepatic glutathione levels.

Effects of lead treatment on intracellular iron and copper concentrations in cultured astroglia

Astroglia are implicated in the pathogenesis of lead (Pb) neurotoxicity in two capacities: as a lead sink that sequesters lead and as a target for direct cellular damage. A proposed cellular mechanism of Pb neurotoxicity is the alteration of metal concentrations, particularly the intracellular accumulation of Cu2+. We measured Pb uptake and the effects of Pb acetate on intracellular trace metal concentrations in astroglial cultures prepared from 0- to 4-day-old rat cerebral hemispheres. Mature Sprague Dawley and immature Wistar rat astroglia in culture took up lead from the medium. This finding replicates in vitro the finding reported by others that astroglia in the brain take up Pb. Intracellular Cu and Fe concentrations (micrograms per 2 x 10(6) cells) were increased fourfold or more by treatment with 100 microM Pb for 3 days in the cultures of immature astroglia. Cu levels were also increased twofold or more in mature astroglia treated for 1-3 days with 100 microM Pb. The significance of this finding is that Cu is a potent inhibitor of Na+, K+-ATPase, an enzyme by which astroglia are thought to remove K+ from the extracellular fluid in the brain. Thus, this finding supports the hypothesis that elevated [Cu], and perhaps [Fe], is a subcellular mechanism of neurotoxicity.

Kinetic parameters of the inhibition of red blood cell aminolevulinic acid dehydratase by triethyl lead and its reversal by dithiothreitol and zinc

In chronic or acute exposure to triethyl lead, a de novo synthesis of aminolevulinic acid dehydratase (delta-ALAD) in bone marrow and an increased activity in circulating red blood cells can be demonstrated by activating the enzyme with dithiothreitol (DTT) and zinc. We determined the median inhibitory concentration and the apparent inhibition constant for triethyl lead on delta-ALAD. After dosing with triethyl lead, in vivo inhibition of ALAD only occurred at the high dose, but activation analysis in vitro showed increased ALAD activity to be present at all dose levels in a dose-dependent fashion. The use of an activation assay for red blood cell ALAD may have value as a bio-effects monitor of exposure to organic lead.

Effect of triethyl lead chloride on delta-aminolevulinic acid dehydratase

The effect of various organic metal compounds on delta-aminolevulinic acid dehydratase (ALAD, porphobilinogen synthetase) activity has been studied. Various organic tin and lead compounds have little effect on this enzyme. However, triethyl lead chloride has a potency similar to that of inorganic lead nitrate in inhibiting ALAD both for in vitro study and after in vivo dosing. Liver and blood ALAD have a similar sensitivity to lead compounds, which is reduced in the presence of zinc. Trimethyl lead chloride inhibits ALAD in vitro to a lesser extent. The results suggest that amphiphilic organic lead compounds may directly inhibit ALAD without prior degradation to inorganic lead. The diffusibility and persistence of triethyl lead combine to make it an especially hazardous lead compound.