Haplotypes of vitamin D receptor modulate the circulating levels of lead in exposed subjects

Genetic factors influence whole blood lead (Pb-B) concentrations in lead exposed subjects. This study aimed at examining the combined effects (haplotype analysis) of three polymorphisms (BsmI, ApaI and FokI) in vitamin D receptor (VDR) gene on Pb-B and on the concentrations of lead in plasma (Pb-P), which is more relevant to lead toxicity, in 150 environmentally exposed subjects. Genotypes were determined by RFLP, and Pb-P and Pb-B were determined by inductively coupled plasma mass spectrometry and by graphite furnace atomic absorption spectrometry, respectively. Subjects with the bb (BsmI polymorphism) or ff (FokI polymorphism) genotypes have lower B-Pb than subjects in the other genotype groups. Subjects with the aa (ApaI polymorphism) or ff genotypes have lower P-Pb than subjects in the other genotype groups. Lower Pb-P, Pb-B, and %Pb-P/Pb-B levels were found in subjects with the haplotype combining the a, b, and f alleles for the ApaI, BsmI, and FokI polymorphisms, respectively, compared with the other haplotype groups, thus suggesting that VDR haplotypes modulate the circulating levels of lead in exposed subjects.     

Effect of food intake on blood lead concentration in workers occupationally exposed to lead

Results from a cross-sectional study showed the concentration of lead in the blood of male workers, aged 20-55 years, occupationally exposed to lead in a steel factory, to be negatively correlated with the daily nutritional content of dietary fiber, iron and vitamin B1 (thiamine) intake. Furthermore, in experiments with rats injected subcutaneously with lead acetate, lead levels in blood and femur of animals on a vitamin-rich laboratory chow were lower than those fed a general laboratory chow. Moreover, in the group fed the vitamin-rich chow, lead excretion in feces increased, while excretion in urine did not. These results suggest that lead excretion from the body may be increased by a high intake of nutrients such as thiamine, iron and fiber, that lead excretion in feces via bile may be enhanced by a large intake of vitamins such as thiamine and that accordingly the lead concentration in the blood of the workers is reduced.     

Evaluation of cerebrospinal fluid concentration and plasma free concentration as a surrogate measurement for brain free concentration.

This study was designed to evaluate the use of cerebrospinal fluid (CSF) drug concentration and plasma unbound concentration (C(u,plasma)) to predict brain unbound concentration (C(u,brain)). The concentration-time profiles in CSF, plasma, and brain of seven model compounds were determined after subcutaneous administration in rats. The C(u,brain) was estimated from the product of total brain concentrations and unbound fractions, which were determined using brain tissue slice and brain homogenate methods. For theobromine, theophylline, caffeine, fluoxetine, and propranolol, which represent rapid brain penetration compounds with a simple diffusion mechanism, the ratios of the area under the curve of C(u,brain)/C(CSF) and C(u,brain)/C(u,plasma) were 0.27 to 1.5 and 0.29 to 2.1, respectively, using the brain slice method, and were 0.27 to 2.9 and 0.36 to 3.9, respectively, using the brain homogenate method. A P-glycoprotein substrate, CP-141938 (methoxy-3-[(2-phenyl-piperadinyl-3-amino)-methyl]-phenyl-N-methyl-methane-sulfonamide), had C(u,brain)/C(CSF) and C(u,brain)/C(u,plasma) ratios of 0.57 and 0.066, using the brain slice method, and 1.1 and 0.13, using the brain homogenate method, respectively. The slow brain-penetrating compound, N[3-(4'-fluorophenyl)-3-(4'-phenylphenoxy)propyl-]sarcosine, had C(u,brain)/C(CSF) and C(u,brain)/C(u,plasma) ratios of 0.94 and 0.12 using the brain slice method and 0.15 and 0.018 using the brain homogenate method, respectively. Therefore, for quick brain penetration with simple diffusion mechanism compounds, C(CSF) and C(u,plasma) represent C(u,brain) equally well; for efflux substrates or slow brain penetration compounds, C(CSF) appears to be equivalent to or more accurate than C(u,plasma) to represent C(u,brain). Thus, we hypothesize that C(CSF) is equivalent to or better than C(u,plasma) to predict C(u,brain). This hypothesis is supported by the literature data.     

The use of a side effect as a qualitative indicator of plasma chlorpromazine levels.

Chlorpromazine (CPZ) is widely used in South African hospitals. The purpose of this study was to determine whether any physiological parameter (side-effect) could be correlated with plasma concentrations of CPZ or its metabolites. In the absence of a blood level, such a correlation could serve as a qualitative indicator of the amount of chlorpromazine in the body. Such a marker can assist the psychiatrist with therapeutic decisions regarding poor compliance and the lack of response with the drug. Fifteen schizophrenic patients were included in this study and regression analysis was used to determine any correlation between CPZ, 7-hydroxychlorpromazine, Chlorpromazine-N-oxide, Nor1 chlorpromazine, Nor2 chlorpromazine, chlorpromazine sulfoxide, Nor2 chlorpromazine sulfoxide and blood pressure, pulse rate, sedation and finger tremor. No correlation was seen between blood pressure or pulse rate and plasma concentrations of CPZ or the metabolites. A good correlation was seen between sedation, 7- hydroxychlorpromazine (P=0.035) and chlorpromazine sulfoxide (P=0.016). The results suggest that as the levels of chlorpromazine sulfoxide increase, the probability of sedation increases, while increasing levels of 7-hydroxychlorpromazine have the opposite effect. A good correlation was also seen between finger tremor and chlorpromazine levels (P=0.035). These results suggest that there is a 50% probability that the patient would experience finger tremor when the plasma concentration of chlorpromazine is 46 ng/ml. This study demonstrated the potential for the use of sedation and finger tremor as qualitative indicators of the plasma concentration of CPZ and two metabolites. Further studies with larger patient numbers are warranted.     

Effect of lead on the levels of some immunoregulatory cytokines in occupationally exposed workers

Lead (Pb) may affect humoral and cellular immunity, acting on lymphocytes as well as on granulocytes and monocytes. Cytokines and nitric oxide (NO) play a central role in the immune balance. In this study, plasma levels of nitrites and nitrates (NOx), IL2, IL4, IL6, IL10, TNF-alpha and INF-gamma, were measured in healthy workers with very low (Pb-B=3.2-18.0 microg/dL) and low (Pb-B=9.1-46.0 microg/dL) Pb-exposure compared to non-exposed workers. Low Pb-exposed workers (Pb-B=9.1 -46.0 microg/ dL) were found to have significantly higher plasma IL-10 levels, and tendentially higher plasma TNF-alpha levels compared to non-exposed workers. This is the first report of a significant increase of plasma IL-10 levels in Pb-exposed workers. Plasma IL-10 increase was influenced by blood Pb levels even after correction for main confounding factors. No difference was found in plasma NOx levels between Pb-exposed and non-exposed workers, which is in agreement with previous findings exclusively regarding groups in the general population. Low Pb-exposure can induce an increase of pro-inflammatory cytokines, such as TNF-alpha, with a consequent increase of other cytokines, such as IL-10, considered a T cell cross-regulatory factor, suggesting possible interference of Pb in the system of immunophlogosis.     

苯并[a]芘和铅对小鼠的联合神经毒性及脑组织的影响

目的研究苯并[a]芘(benzo[a]pyrene BaP)、铅单独与联合作用对小鼠的神经毒性及小鼠脑组织热应激蛋白(HSPs)HSP 70、HSP 90β表达的影响。方法将80只昆明种小鼠随机分为10组，每组8只，既：空白对照组、溶剂对照组、低浓度铅染毒组、高浓度铅染毒组、低剂量BaP染毒组、高剂量BaP染毒组、低浓度铅 低剂量BaP染毒组、低浓度铅 高剂量BaP染毒组、高浓度铅 低剂量BaP联合染毒组和高浓度铅 高剂量BaP联合染毒组。低、高剂量BaP染毒分别为0．5和5mg／kg BaP的植物油溶剂每周4次腹腔注射，溶剂对照组用植物油作平行处理。低、高剂量的铅染毒分别为5．4和54mg／L醋酸铅饮水染毒。实验中观察动物一般情况及神经系统损伤表现，实验8周后取各组小鼠脑组织，称重并计算脑组织脏器系数。制作脑组织混合匀浆，western blot法检测HSP70、HSP90β水平。结果BaP与铅联合染毒可使小鼠脑组织脏器系数降低；HSP900β相对表达值与脑组织脏器系数量负相关。结论BaP与铅联合作用可明显损伤脑组织；HSP90β对上述损害起标志作用。     

Evaluation of pteridine metabolism in battery workers chronically exposed to lead

Occupationally-exposed lead affects the neuromuscular junction and might cause disturbances in the locomotor activity. This study was undertaken to evaluate pteridine metabolism, in which neurotransmitters are synthesized in battery workers. Urinary neopterin, biopterin and creatinine were measured using high performance liquid chromatography. Serum neopterin concentrations were detected by enzyme-linked immunoassay. Blood dihydropteridine reductase (DHPR) activities and deltaaminolevulinic acid (delta-ALA) were measured spectrophotometrically. Blood and urinary lead were detected by atomic absorption spectroscopy. Significantly increased blood and urinary lead levels, urinary neopterin, biopterin and delta-ALA were found in workers, while DHPR activities were indifferent compared to control group. Urinary creatinine decreased. This is the first study to demonstrate that increased activity of the pteridine pathway results in the accumulation of the neurotransmitters that may be responsible for the neurological disorders.     

CGRP and ET-1 plasma levels in normal subjects

OBJECTIVE: Calcitonin gene-related peptide (CGRP) is a 37 amino acid peptide displaying about 50% homology with amylin which is secreted from the pancreatic islets of Langerhans. The main form, the beta-CGRP, is produced by the enteric nervous system and perivascular nerves of the vasa-vasorum. It represents one of the most powerful vasodilator yet discovered but its role is not yet completely clarified. High levels of this peptide have been shown in patients affected with thyroid medullary carcinoma, phaemocromocytoma and lung carcinoma. Recently circulating levels of CGRP have been found in normal subjects. Endothelin-1 (ET-1), a potent vasoconstrictor peptide, isolated from porcine endothelial cells, is an important regulator of the vascular tone acting in physiological antagonism with atrial natriuretic hormone (ANH). With this study we intended to investigate the presence of any correlation between CGRP and ET-1 in normal subjects. PATIENTS: For the study we considered 20 normal subjects (11 males and 9 females) aged 23 to 50. MEASURES: Plasma levels of CGRP and ET-1 were measured by radioimmunological Kit. RESULTS: A positive and significant correlation between calcitonin gene-related peptide and endothelin-1 was found. CONCLUSIONS: Our results confirms that CGRP and ET-1 have opposing actions on vessels and that they can act together in haemodinamic regulation.     

Cyanide adducts with human plasma proteins: albumin as a potential exposure surrogate

Cyanide (CN) is a ubiquitous environmental toxicant. The measurement of CN in whole blood is a common exposure assay, but values are error prone because of CN's rapid metabolism and clearance (t1/2 < 1 h) from this compartment. This study was undertaken to determine whether CN forms covalent adduct(s) with plasma proteins that could serve as stable biomarker(s) and potential surrogate(s) of exposure. When added to human blood, plasma, or serum, CN formed covalent adducts with immunoglobulin G (IgG) and serum albumin (HSA) in the plasma fraction. Covalent adducts were not detected in the cellular, primarily erythrocyte, fraction. With human, mouse, and rabbit IgGs, the reaction with CN occurred at intra- and/or interchain disulfide linkages in the heavy and light chains. Digestion of CN-treated HSA with trypsin or the endoproteinase Lys-C at basic pH produced tautomeric 2-iminothiazoline-4-carboxylyl/2-aminothiazolidine-4-carboxylyl (itcCys) N-terminal peptides exclusively, consistent with prior model peptide/protein studies showing that under basic conditions internal S-cyanylated-Cys residues cyclize with concomitant release of the upstream peptide. The most readily detectable reaction of CN with purified HSA was at Cys34, the only Cys of the 35 present not connected as internal cystines. Because CN does not react with free sulfhydryl groups, it is probable that S-cyanylation at Cys34 occurs at those residues that carry GSH, Cys, or other small molecules as mixed disulfides. Relatively less detectable, modified Cys residues were also identified at positions 53, 124, 392, 477, and 487. When 14CN was added to human serum or whole blood at concentrations spanning a putative nontoxic to lethal range, stable adduct formation with HSA occurred in a linear, concentration-dependent reaction that was complete within 2 h. These attributes of the reaction, coupled with a plasma compartment location, suggest that quantitation of CN bound to HSA would provide a much more reliable assessment of exposure than does measurement of CN in blood.     

Erythrocyte acetylcholinesterase activity as a surrogate indicator of lead-induced neurotoxicity in occupational lead exposure in Abeokuta, Nigeria

Dose-effect and dose-response relationships in occupational neurotoxicology are rarely studied by means of biochemical methods. In order to investigate the potential neurotoxic effects of lead during occupational exposure to this metal, the activity of erythrocyte acetylcholinesterase (AcChE), as well as blood pressure and pulse, were determined in various artisans in Abeokuta, Nigeria, who have been shown to be occupationally exposed to lead, and these were related to blood lead levels. AcChE activity in the artisans was inhibited to varying extents. While AcChE activity was inhibited to the tune of 39% in the male petrol station attendants, the inhibition amounted to 32% in female petrol station attendants. In other artisans, AcChE inhibition ranged from 31% in the welders to 38% in painters. The lowest inhibition of 15% was obtained in the panel beaters. Correlations, as calculated by Pearson's method, revealed a significant (p<0.001) inverse linear relationship between AcChE activity and blood lead levels (r=-0.40; y=-120.38x+13935.59; p<0.001). Blood pressure and pulse were not significantly different between control and lead-exposed subjects. Our findings suggest that erythrocyte AcChE activity could be used as a biomarker of lead-induced neurotoxicity in occupationally exposed subjects.     

Marihuana attenuates the rise in plasma ethanol levels in human subjects.

This study was conducted to determine if plasma ethanol levels are altered as a result of smoking marihuana. Fifteen healthy adult male volunteers who used ethanol and marihuana on a casual basis participated in this study. Subjects were randomly assigned to one of three groups: placebo, low-dose, or high-dose marihuana. The marihuana dose was held constant and each subject drank three different doses of ethanol on 3 separate days spaced at least 1 week apart. Subjects drank either placebo or ethanol at doses of 0.35 g/kg (7.60 mmol/kg) or 0.70 g/kg (15.19 mmol/kg). Thirty minutes after drinking they smoked either a placebo marihuana cigarette, or one containing either 1.26% or 2.53% delta 9-tetrahydrocannabinol. Plasma ethanol levels rose sharply after the 0.7 g/kg dose and peaked at 50 minutes after drinking began (78.25 +/- 4.95 mg/dl). When subjects smoked the high-dose marihuana cigarettes after the 0.7 g/kg dose of ethanol, peak plasma ethanols levels were only 54.80 +/- 8.32 mg/dl at 105 minutes after drinking began. These alterations in plasma ethanol levels paralleled a reduction in the duration of ethanol- and marihuana-induced subjective effects after high doses of both drugs. These data suggest that marihuana may alter ethanol bioavailability.     

Biological levels of cadmium and zinc in the small intestine of non-occupationally exposed human subjects

The objective of this study was to estimate the relationships between cadmium (Cd) levels in the small intestine and other organs (kidney, liver, lungs) and factors influencing the intestinal Cd levels in humans, as based on autopsy analysis of subjects not exposed to Cd occupationally. The study also involved estimating the levels of zinc (Zn) in these organs, as it is known that this element exerts interactions with Cd at the level of absorption and tissue binding. The levels of Cd and Zn were determined in the renal cortex, liver, lungs and three fragments of the small intestine (duodenum, jejunum, ileum) of 29 subjects deceased at the age 42 +/- 13 years. Flame atomic absorption spectrometry (AAS; kidneys, liver) and flameless AAS (lungs, intestine) were used. The level of Cd in the lungs was used as a marker of smoking habit. The determined levels (mean +/- SD) were: 0.28 +/- 0.16 microg Cd/g and 15.2 +/- 3.4 microg Zn/g in the duodenum; 0.26 +/- 0.15 microg Cd/g and 16.9 +/- 3.7 microg Zn/g in the jejunum; 0.13 +/- 0.07 microg Cd/g and 14.6 +/- 5.4 microg Zn/g in the ileum. Intestinal Cd levels are correlated with organ and total body Cd, and this was best expressed for Cd in ileum (r=0.67 with renal, r=0.71 with hepatic and r=0.68 with total Cd). In conclusions, the levels of Cd in the small intestine of humans are relatively low and reflect predominantly the whole body retention of this element. Somewhat higher levels of Cd are contained in the initial parts of the small intestines. In all fragments of small intestines the levels of Cd are higher in smokers. Also, the levels of Zn were relatively low and did not correlate with the levels of Cd.     

Industrial lead exposure: a review of blood lead levels in South Island industries, 1974-83

Relative risks of increased lead absorption found in 31 occupations were investigated. Serial red cell lead measurements on 1319 males and 186 females provided a mean and range for each occupational type. The magnitude of the mean and percentage of raised levels identified the degree of occupational risk. The mean red cell lead for 50% of employees was within the regional usual range for those not occupationally exposed. In 77% the mean red cell lead was less than 4.1 mumol/l. Of the remainder, 4% had levels greater than 5.7 mumol/l and 1% had levels greater than 7.7 mumol/l. Our findings have been used to manage local chronic and acute lead problems.     

Operant behavior of rats exposed to lead before or after weaning

Rats were exposed to lead (Pb) before or after weaning. For preweaning exposures, nursing dams received 0.2% Pb acetate(1090 ppm Pb) in drinking water. Offspring treated after weaning consumed the same concentration. Tapwater served as the control fluid. Pre-post treatments were distributed among four experimental groups of 10 rats each: tap water-tap water, Pb-tap water, tap water-Pb, Pb-Pb. Operant behavior training began on Postnatal Day 58. Animals performed on a multiple reinforcement schedule of food presentation consisting of fixed-interval, fixedratio, and time out components. Statistical analyses of experimental sessions 4 to 11 (Postnatal Days 72 to 79) revealed that postweaning exposure significantly lengthened the median interval (interresponse time) between consecutive responses on both the interval and ratio schedules. Preweaning exposure alone tended to produce a shortening of the median interresponse time. Other performance indices and subsequent variations of ratio size showed similar but not significantly different relationships among the treatment groups. No significant histopathology was detected. Brain and blood Pb concentrations were consistent with the treatment protocol.     

Neonatal lead exposure in the rat: Decreased learning as a function of age and blood lead concentrations

Suckling rats were treated with lead both through the milk of lead-treated dams and direct injection ip. Lead was administered daily to three age groups: group 1 from Days 1–10; group 2 from Days 11–20; group 3 from Days 1–20; and learning was measured by use of the T-maze in all groups at 8–10 wk of age. Organ weights, body weights, and blood lead concentrations were determined in suckling, weanling, and 10-wk-old rats. Learning ability was decreased in 8- to 10-week-old male and female rats which had been nursed 20 days by dams treated with 17.5 or 25 mg Pb/kg daily after parturition. Administration of lead to the dam 1–10 days similarly decreased learning, but administration 11–20 days did not. None of the doses used produced overt signs of lead toxicity, altered growth rate, or altered organ-to-body-weight ratios in either the pups or the dams. Blood lead concentrations were increased in the pup at 11 days but not at 21 days or 10 wk (45.8 ± 2.0; 20.4 ± 2.0, and 23.4 ± 2.4 μg/100 ml, respectively; mean ± SE). These results show that the brain of the 1- to 10-day-old suckling rat pup is particularly sensitive to lead exposure with residual effects produced on learning present in the 8- to 10-wk-old adult after blood lead concentrations have returned to control values.