1
|
Meek EC, Carr RL, Chambers JE. In vitro age-related differences in rats to organophosphates. Toxicol In Vitro 2021; 72:105102. [PMID: 33497710 PMCID: PMC7928206 DOI: 10.1016/j.tiv.2021.105102] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 01/08/2021] [Accepted: 01/20/2021] [Indexed: 02/05/2023]
Abstract
The mechanism of toxic action for organophosphates (OPs) is the persistent inhibition of acetylcholinesterase (AChE) resulting in accumulation of acetylcholine and subsequent hyperstimulation of the nervous system. Organophosphates display a wide range of acute toxicities. Differences in the OP's chemistries results in differences in the compound's metabolism and toxicity. Acute toxicities of OPs appear to be principally dependent on compound specific efficiencies of detoxication, and less dependent upon efficiencies of bioactivation and sensitivity of AChE. Serine esterases, such as carboxylesterase (CaE) and butyrylcholinesterase (BChE), play a prominent role in OP detoxication. Organophosphates can stoichiometrically inhibit these enzymes, removing OPs from circulation thus providing protection for the target enzyme, AChE. This in vitro study investigated age-related sensitivity of AChE, BChE and CaE to twelve structurally different OPs in rat tissues. Sensitivity of esterases to these OPs was assessed by inhibitory concentration 50s (IC50s). The OPs displayed a wide range of inhibitory potency toward AChE with IC50s in the low nM-μM range with no differences among ages; however, the CaE IC50s generally increased with age reflecting greater protection in adults. These results suggest age-related differences in acute toxicities of OPs in mammals are primarily a result of their detoxication capacities.
Collapse
Affiliation(s)
- Edward C Meek
- Center for Environmental Health Sciences and Department of Comparative Biomedical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762, United States of America.
| | - Russell L Carr
- Center for Environmental Health Sciences and Department of Comparative Biomedical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762, United States of America.
| | - Janice E Chambers
- Center for Environmental Health Sciences and Department of Comparative Biomedical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762, United States of America.
| |
Collapse
|
2
|
Smith CD, Wright LKM, Garcia GE, Lee RB, Lumley LA. Hormone-dependence of sarin lethality in rats: Sex differences and stage of the estrous cycle. Toxicol Appl Pharmacol 2015; 287:253-7. [PMID: 26079828 DOI: 10.1016/j.taap.2015.06.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Revised: 06/08/2015] [Accepted: 06/10/2015] [Indexed: 11/18/2022]
Abstract
Chemical warfare nerve agents (CWNAs) are highly toxic compounds that cause a cascade of symptoms and death, if exposed casualties are left untreated. Numerous rodent models have investigated the toxicity and mechanisms of toxicity of CWNAs, but most are limited to male subjects. Given the profound physiological effects of circulating gonadal hormones in female rodents, it is possible that the daily cyclical fluctuations of these hormones affect females' sensitivity to the lethal effects of CWNAs, and previous reports that included female subjects did not control for the stage of the hormonal cycle. The aim of the current study was to determine the 24-hour median lethal dose (LD50) of the CWNA sarin in male, ovariectomized (OVEX) female, and female rats during different stages of the estrous cycle (diestrus, proestrus, and estrus). Additionally, baseline activity levels of plasma acetylcholinesterase, butyrylcholinesterase, and carboxylesterase were measured to determine differences among the groups. Results indicated that females in proestrus had a significantly higher LD50 of sarin compared to OVEX and estrous females. Although some sex differences were observed in the activity levels of plasma esterases, they were not consistent and likely not large enough to significantly affect the LD50s. These results suggest that hormonal cyclicity can influence the outcome of CWNA-related studies using female rodents, and that this variability can be minimized by controlling for the stage of the cycle. Additional research is necessary to determine the precise mechanism of the observed differences because it is unlikely to be solely explained by plasma esterase activity.
Collapse
Affiliation(s)
- Carl D Smith
- US Army Medical Research Institute of Chemical Defense (USAMRICD), Aberdeen Proving Ground, MD 21010, United States.
| | - Linnzi K M Wright
- US Army Medical Research Institute of Chemical Defense (USAMRICD), Aberdeen Proving Ground, MD 21010, United States
| | - Gregory E Garcia
- US Army Medical Research Institute of Chemical Defense (USAMRICD), Aberdeen Proving Ground, MD 21010, United States
| | - Robyn B Lee
- US Army Medical Research Institute of Chemical Defense (USAMRICD), Aberdeen Proving Ground, MD 21010, United States
| | - Lucille A Lumley
- US Army Medical Research Institute of Chemical Defense (USAMRICD), Aberdeen Proving Ground, MD 21010, United States
| |
Collapse
|
3
|
Muller M, Hess L, Tardivo A, Lajmanovich R, Attademo A, Poletta G, Simoniello MF, Yodice A, Lavarello S, Chialvo D, Scremin O. Neurologic dysfunction and genotoxicity induced by low levels of chlorpyrifos. Neurotoxicology 2014; 45:22-30. [PMID: 25196089 DOI: 10.1016/j.neuro.2014.08.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Revised: 08/05/2014] [Accepted: 08/26/2014] [Indexed: 11/19/2022]
Abstract
Chlorpyrifos (CPF) is an organophosphorus cholinesterase inhibitor widely used as an insecticide. Neuro and genotoxicity of this agent were evaluated following daily subcutaneous injections at 0.1, 1 and 10mg/kg or its vehicle to laboratory rats during one week, at the end of which somatosensory evoked potentials (SEP) and power spectrum of the electroencephalogram (EEGp) were recorded under urethane anesthesia. In another group of conscious animals, auditory startle reflex (ASR) was evaluated followed, after euthanasia, with measurements of plasma B-esterases, and genotoxicity with the alkaline comet assay (ACA) at the same CPF doses. The results indicated a CPF dose related inhibition of B-esterases. Enhanced inhibition of the ASR by a subthreshold pre-pulse was observed at all doses and ACA showed a significant higher DNA damage than vehicle controls in animals exposed to 10mg/kg CPF. A trend to higher frequencies of EEGp and an increase in amplitude of the first negative wave of the SEP were found at all doses. The first positive wave of the SEP decreased at the CPF dose of 10mg/kg. In summary, a shift to higher EEG frequencies and alterations of somatosensory and auditory input to the central nervous system were sensitive manifestations of CPF toxicity, associated with depression of B-esterases. The changes in electrical activity of the cerebral cortex and DNA damage observed at doses that do not elicit overt toxicity may be useful in the detection of CPF exposure before clinical signs appear.
Collapse
Affiliation(s)
- Mariel Muller
- PROFISIO, Facultad de Ciencias Medicas, Universidad Nacional de Rosario, Santa Fe 3100, Rosario, Argentina
| | - Leonardo Hess
- PROFISIO, Facultad de Ciencias Medicas, Universidad Nacional de Rosario, Santa Fe 3100, Rosario, Argentina
| | - Agostina Tardivo
- PROFISIO, Facultad de Ciencias Medicas, Universidad Nacional de Rosario, Santa Fe 3100, Rosario, Argentina
| | - Rafael Lajmanovich
- Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria, Paraje El Pozo, Santa Fe, Argentina; Consejo Nacional de Investigaciones Cientificas y Tecnicas, Argentina
| | - Andres Attademo
- Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria, Paraje El Pozo, Santa Fe, Argentina; Consejo Nacional de Investigaciones Cientificas y Tecnicas, Argentina
| | - Gisela Poletta
- Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria, Paraje El Pozo, Santa Fe, Argentina; Consejo Nacional de Investigaciones Cientificas y Tecnicas, Argentina
| | - Maria Fernanda Simoniello
- Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria, Paraje El Pozo, Santa Fe, Argentina
| | - Agustina Yodice
- PROFISIO, Facultad de Ciencias Medicas, Universidad Nacional de Rosario, Santa Fe 3100, Rosario, Argentina
| | - Simona Lavarello
- PROFISIO, Facultad de Ciencias Medicas, Universidad Nacional de Rosario, Santa Fe 3100, Rosario, Argentina
| | - Dante Chialvo
- PROFISIO, Facultad de Ciencias Medicas, Universidad Nacional de Rosario, Santa Fe 3100, Rosario, Argentina; Consejo Nacional de Investigaciones Cientificas y Tecnicas, Argentina
| | - Oscar Scremin
- PROFISIO, Facultad de Ciencias Medicas, Universidad Nacional de Rosario, Santa Fe 3100, Rosario, Argentina; Consejo Nacional de Investigaciones Cientificas y Tecnicas, Argentina; Greater Los Angeles VA Healthcare System and David Geffen School of Medicine at UCLA, 11301 Wilshire Building, Los Angeles, CA 90073, USA.
| |
Collapse
|
4
|
Abstract
Acetylcholinesterase, butyrylcholinesterase, carboxylesterase, and paraoxonase activities in human, mouse, and rat blood were measured. The proportions of these enzymes activities differed significantly. In humans, the most significant were cholinesterase activities, while in rats and mice the contribution of carboxylesterase activity was the greatest. High arylesterase activity of paraoxonase was observed in all cases. Species-specific differences should be taken into consideration when carrying out preclinical trials on rodents for optimization of the pharmacokinetic characteristics of drugs containing complex ester groups.
Collapse
Affiliation(s)
- E V Rudakova
- Laboratory of Molecular Toxicology, Institute of Physiologically Active Substances, Russian Academy of Sciences, Chernogolovka, Moscow Region, Russia.
| | | | | |
Collapse
|
5
|
Borecki IB, Rice T, Pérusse L, Bouchard C, Rao DC. An Exploratory Investigation of Genetic Linkage with Body Composition and Fatness Phenotypes: The Québec Family Study. ACTA ACUST UNITED AC 2012; 2:213-9. [PMID: 16355479 DOI: 10.1002/j.1550-8528.1994.tb00050.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In the present investigation, we have attempted to identify regions of the genome in which "obesity genes" potentially reside using robust sib-pair linkage analysis. Data were collected on 1,628 individuals in 301 nuclear families residing in the environs of Québec City during the period 1978-1981. In addition to traditional blood group antigens and enzyme polymorphisms, several phenotypes in the obesity domain that are associated with increased morbidity were assessed, including measures relating to heaviness (i.e., the body mass index), body composition and nutrient partitioning (i.e., % body fat), and regional fat distribution without and with standardization for total fat mass (i.e., the sum of six skinfold thicknesses, and the ratio of the sums of trunk to extremity skinfold thicknesses). Three consistent patterns of potential linkage relationships with obesity phenotypes were revealed in these data, involving the marker loci adenosine deaminase, the Kell blood group antigen, and esterase D, which identify chromosomal regions 20q13, 7q33, and 13q14, respectively. Other potential linkages also were identified in the short arm of chromosome 1, interesting because of the presence of the db and fa loci on homologous regions of chromosome 1 in mouse and rat models of obesity, respectively. Each of the tentative linkage relationships reported here warrant follow-up using alternative methods and require replication in independent studies.
Collapse
Affiliation(s)
- I B Borecki
- Division of Biostatistics, Washington University School of Medicine, Box 8067, 660 S. Euclid Ave., St. Louis, MO 63110, USA
| | | | | | | | | |
Collapse
|
6
|
Basso A, Attademo AM, Lajmanovich RC, Peltzer PM, Junges C, Cabagna MC, Fiorenza GS, Sanchez-Hernandez JC. Plasma esterases in the tegu lizard Tupinambis merianae (Reptilia, Teiidae): impact of developmental stage, sex, and organophosphorus in vitro exposure. Environ Sci Pollut Res Int 2012; 19:214-225. [PMID: 21717171 DOI: 10.1007/s11356-011-0549-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Accepted: 06/13/2011] [Indexed: 05/31/2023]
Abstract
PURPOSE In this study, we determined normal serum butyrylcholinesterase (BChE) and carboxylesterase (CbE) activities in Tupinambis merianae in order to obtain reference values for organophosphorus pesticide monitoring. METHODS Forty-two T. merianae individuals were grouped by sex and size to identify potential differences in their enzyme levels to allow for proper representation of normal values for females, males, juveniles, and hatchlings. Mean CbE was determined using two model substrates: alpha-naphtylacetate (α-NA) and p-nitrophenyl valerate (4-NPV). BChE and CbE sensitivity to malaoxon (Mx) was also evaluated as well as the possibility of BChE reactivation with pyridine-2-aldoxime methochloride (2-PAM). RESULTS Mean adult females' BChE was significantly higher than adult males, juveniles, and hatchlings. No significant differences were found between groups regarding CbE. CbE (4-NPV) activity showed slightly negative correlation with lizard snout-vent length, while BChE and CbE (α-NA) showed no correlation with body size. Apparent IC(50) values for BChE and CbE (α-NA) suggested different sensitivities among groups. CbE (4-NPV) could not be inhibited. All Mx-inhibited groups treated with 2-PAM in a final concentration of 2.8 mM showed clear signs of reactivation. CONCLUSIONS In conclusion, the results demonstrate that (1) plasma esterase activity did not vary with age and sex, except for BChE activity, and (2) because biological and environmental variables could be confounding factors in the response of plasma cholinesterases, complementary biomarkers like CbE inhibition and oxime-induced reactivation of esterases are strongly recommended.
Collapse
Affiliation(s)
- Agustín Basso
- Faculty of Biochemistry and Biological Sciences-FBCB-UNL, Santa Fe, Argentina.
| | | | | | | | | | | | | | | |
Collapse
|
7
|
Thangthaeng N, Sumien N, Forster MJ, Shah RA, Yan LJ. Nongradient blue native gel analysis of serum proteins and in-gel detection of serum esterase activities. J Chromatogr B Analyt Technol Biomed Life Sci 2011; 879:386-94. [PMID: 21237726 PMCID: PMC3034814 DOI: 10.1016/j.jchromb.2010.12.026] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Revised: 12/22/2010] [Accepted: 12/23/2010] [Indexed: 12/21/2022]
Abstract
The objective of the present study was to analyze serum protein complexes and detect serum esterase activities using nongradient blue native polyacrylamide gel electrophoresis (BN-PAGE). For analysis of potential protein complexes, serum from rat was used. Results demonstrate that a total of 8 gel bands could be clearly distinguished after Coomassie blue staining, and serum albumin could be isolated nearly as a pure protein. Moreover, proteins in these bands were identified by electrospray mass spectrometry and low-energy collision induced dissociation (CID)-MS/MS peptide sequencing and the existence of serum dihydrolipoamide dehydrogenase (DLDH) was confirmed. For studies of in-gel detection of esterase activities, serum from rat, mouse, and human was used. In-gel staining of esterase activity was achieved by the use of either α-naphthylacetate or β-naphthylacetate in the presence of Fast blue BB salt. There were three bands exhibiting esterase activities in the serum of both rat and mouse. In contrast, there was only one band showing esterase activity staining in the human serum. When serum samples were treated with varying concentrations of urea, esterase activity staining was abolished for all the bands except the one containing esterase 1 (Es1) protein that is known to be a single polypeptide enzyme, indicating that majority of these esterases were protein complexes or multimeric proteins. We also identified the human serum esterase as butyrylcholinesterase following isolation and partial purification using ammonium sulfate fractioning and ion exchange column chromatographies. Where applicable, demonstrations of the gel-based method for measuring serum esterase activities under physiological or pathophysiological conditions were illustrated. Results of the present study demonstrate that nongradient BN-PAGE can serve as a feasible analytical tool for proteomic and enzymatic analysis of serum proteins.
Collapse
Affiliation(s)
- Nopporn Thangthaeng
- Department of Pharmacology and Neuroscience and Institute for Aging and Alzheimer’s Disease Research, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Nathalie Sumien
- Department of Pharmacology and Neuroscience and Institute for Aging and Alzheimer’s Disease Research, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Michael J. Forster
- Department of Pharmacology and Neuroscience and Institute for Aging and Alzheimer’s Disease Research, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Ruchir A. Shah
- Department of Pharmacology and Neuroscience and Institute for Aging and Alzheimer’s Disease Research, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Liang-Jun Yan
- Department of Pharmacology and Neuroscience and Institute for Aging and Alzheimer’s Disease Research, University of North Texas Health Science Center, Fort Worth, TX, USA
| |
Collapse
|
8
|
Attademo AM, Cabagna-Zenklusen M, Lajmanovich RC, Peltzer PM, Junges C, Bassó A. B-esterase activities and blood cell morphology in the frog Leptodactylus chaquensis (Amphibia: Leptodactylidae) on rice agroecosystems from Santa Fe Province (Argentina). Ecotoxicology 2011; 20:274-282. [PMID: 21113795 DOI: 10.1007/s10646-010-0579-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 11/16/2010] [Indexed: 05/30/2023]
Abstract
Activity of B-esterases (BChE: butyrylcholinesterase and CbE: carboxylesterase using two model substrates: α-naphthyl acetate and 4-nitrophenyl valerate) in a native frog, Leptodactylus chaquensis from rice fields (RF1: methamidophos and RF2: cypermethrin and endosulfan sprayed by aircraft) and non-contaminated area (pristine forest) was measured. The ability of pyridine-2-aldoxime methochloride (2-PAM) to reactivate BChE levels was also explored. In addition, changes in blood cell morphology and parasite infection were determined. Mean values of plasma BChE activities were lower in samples from the two rice fields than in those from the reference site. CbE (4-nitrophenyl valerate) levels varied in the three sites studied, being highest in RF1. Frog plasma from RF1 showed positive reactivation of BChE activity after incubation with 2-PAM. Blood parameters of frogs from RF2 revealed morphological alterations (anisochromasia and immature erythrocytes frequency). Moreover, a major infection of protozoan Trypanosoma sp. in individuals from the two rice fields was detected. We suggest that integrated use of several biomarkers (BChE and CBEs, chemical reactivation of plasma with 2-PAM, and blood cell parameters) may be a promising procedure for use in biomonitoring programmes to diagnose pesticide exposure of wild populations of this frog and other native anuran species in Argentina.
Collapse
Affiliation(s)
- Andrés M Attademo
- Laboratory of Ecotoxicology, Faculty of Biochemistry and Biological Sciences (ESS-FBCB-UNL), Pje. El Pozo S/N., 3000, Santa Fe, Argentina.
| | | | | | | | | | | |
Collapse
|
9
|
Abstract
Ghrelin circulates as acylated (AG) and unacylated (or desacyl) ghrelin (UAG). We aimed at clarifying the effect of age and sex on plasma deacylation and degradation of AG in vivo and in vitro in the rat. In vivo, we compared AG and UAG concentrations following administration of 1 microg AG intraperitoneally in rat neonates during the first 3h of life. AG administration caused a 2-3 times increase in plasma AG concentrations contrasting with a approximately 1000 times increase in UAG concentrations suggesting rapid deacylation of AG into UAG. In vitro, we demonstrated that AG degradation was greater in the fetus (97% over 30 min) and decreased progressively to 57% in adult animals (P<0.001). Carboxylesterase and butyrylcholinesterase activities were determined during the fetal (day 21 of pregnancy) and postnatal period (days 1, 6, 13, 21 and 28) and in the adult rat and were found to increase with age (P<0.001). While inhibition of carboxylesterase and butyrylcholinesterase did not affect AG deacylation, serine protease inhibitors decreased AG degradation in the adult rat (from 59% to 23%) and, to a lesser extent, in the rat neonate (from 92% to 57%) by reducing both deacylation and degradation into non-UAG metabolites. Our data suggest that degradation of AG into UAG and non-UAG metabolites is much faster in the fetus and in the rat neonate compared to the adult. We speculate that this process allows for fine tuning of the physiological effects of both AG and UAG.
Collapse
Affiliation(s)
- Hehong Ni
- Endocrinology and Diabetes Unit, British Columbia Children's Hospital, University of British Columbia, Vancouver V6H 3V4, Canada
| | | | | |
Collapse
|
10
|
Gafarov NI, Zakharenkov VV, Panev NI, Burdeĭn AV, Puzyrev VP, Rudko AA. [Chronic occupational bronchitis in workers of coal extracting enterprises in Kouzbass: role of endogenous factors]. Med Tr Prom Ekol 2010:37-40. [PMID: 20480820] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The authors studied distribution of biochemical markers for HP, GC, EsD, AcP genes, polymorphism of GSTT1 (GST-theta 1), GSTM1 (GST-mu 1), locus WNTR of NOS3 gene (alleles A/B) in chronic dust bronchitis patients and in apparently healthy individuals. Genotypes EsD 1-2 and AcP bb individuals were proved to be most prone to the disease. Endogenous resistent factors for chronic dust bronchitis are genotypes GC 1-1, EsD 1-1, AcP bc.
Collapse
|
11
|
Li L, Weng W, Harrison EH, Fisher EA. Plasma carboxyl ester lipase activity modulates apolipoprotein B-containing lipoprotein metabolism in a transgenic mouse model. Metabolism 2008; 57:1361-8. [PMID: 18803939 PMCID: PMC2587065 DOI: 10.1016/j.metabol.2008.05.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2007] [Accepted: 05/13/2008] [Indexed: 10/21/2022]
Abstract
Pancreatic carboxyl ester lipase (CEL) is in the plasma of many mammals, including humans and rats, but not mice. In vitro, CEL hydrolyzes cholesterol esters of apolipoprotein B-containing lipoproteins (apo B-Lp). To study the effect of CEL on metabolism of apo B-Lp and atherosclerosis in vivo, apo E-knockout (EKO) mice, which have high plasma levels of apo B-Lp and are prone to atherosclerosis, were made to secrete CEL into plasma by introducing a transgene containing a liver-specific promoter and rat CEL complementary DNA. Plasma CEL activity in EKO-CEL mice was comparable with that found in rats. Evidence of modification of apo B-Lp by plasma CEL in vivo was an increase in the free cholesterol to cholesterol ester ratio of apo B-Lp from mice on chow or a Western-type diet. In addition, plasma total cholesterol levels were elevated in EKO-CEL mice, with the elevation found exclusively in the apo B-Lp fraction. Associated with the increase in steady-state apo B-Lp levels was an increase in the plasma half-life of very low-density lipoproteins (VLDL) in EKO-CEL mice, measured by the clearance rate of injected VLDL. Interestingly, despite the increase of apo B-Lp, the atherosclerotic lesion did not differ between EKO and EKO-CEL mice on a Western-type diet. In summary, our results demonstrate that plasma CEL modulates apo B-Lp metabolism in vivo, resulting in reduced VLDL clearance and elevated plasma cholesterol levels.
Collapse
Affiliation(s)
- Ling Li
- Laboratory of Lipoprotein Research, Cardiovascular Institute, Department of Medicine, Mount Sinai School of Medicine, New York, NY 10029, USA.
| | | | | | | |
Collapse
|
12
|
Attademo AM, Peltzer PM, Lajmanovich RC, Cabagna M, Fiorenza G. Plasma B-esterase and glutathione S-transferase activity in the toad Chaunus schneideri (Amphibia, Anura) inhabiting rice agroecosystems of Argentina. Ecotoxicology 2007; 16:533-9. [PMID: 17701347 DOI: 10.1007/s10646-007-0154-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2007] [Accepted: 06/06/2007] [Indexed: 05/16/2023]
Abstract
B-esterase (BChE: butyrylcholinesterase and CbE: carboxylesterase) and glutathione S-transferase (GST) activity were measured in the plasma of Chaunus schneideri collected in rice fields and surrounding environments and in a reference pristine forest. The chemical criterion based on in-vitro reactivation of BChE activity using pyridine-2-aldoxime methochloride (2-PAM) was also determined. Mean values of plasma BchE, CbE, and GST activity for samples from agricultural areas were different from those for samples from pristine forest. Plasma samples from the two agricultural areas showed positive reactivation of BChE activity after incubation with 2-PAM. Based on our experimental evidence we suggest B-esterases and gluthatione S-transferases can be used in field monitoring as biomarkers of exposure of wildlife to pesticides, because the analysis in non-destructive and is sensitive to anti-ChE agrochemicals. Chemical reactivation of BChE is also a complementary method for assessing the effects of pesticides on toads inhabiting rice fields. Further studies are urgently needed to investigate adverse effects of massive exposure to pesticides experienced by native populations of anurans.
Collapse
|
13
|
Pan H, Kopecková P, Liu J, Wang D, Miller SC, Kopecek J. Stability in plasmas of various species of HPMA copolymer-PGE1 conjugates. Pharm Res 2007; 24:2270-80. [PMID: 17899324 DOI: 10.1007/s11095-007-9449-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2007] [Accepted: 08/28/2007] [Indexed: 10/22/2022]
Abstract
PURPOSE To determine the stability of HPMA copolymer-prostaglandin E(1) (PGE(1)) conjugates in plasmas of different species and to identify the enzymes responsible for the cleavage of the ester bond. METHODS The conjugates were incubated in human, rat, and mouse plasma at 37 degrees C in the presence and absence of specific esterase inhibitors. The released PGE(1) was analyzed using an HPLC assay. To evaluate the effect of the conformation of the conjugate on the rate of PGE(1) release, its structure was modified by the attachment of hydrophobic side chains. RESULTS The rate of PGE(1) release was strongly species dependent. Whereas the conjugate was stable in human plasma, the PGE(1) release in rat or mouse plasma was substantial. In rat plasma, the ester bond cleavage was mainly catalyzed by butyrylcholinesterase; in mouse plasma, in addition to butyrylcholinesterase, carboxylesterase also contributed to the cleavage. The formation of compact polymer coils stabilized the ester bond. CONCLUSIONS HPMA copolymer-PGE(1) conjugates are strong candidates as novel therapeutics for the treatment of osteoporosis. The observed species differences in plasma stability of ester bonds are of importance, because the ovariectomized rat model is recommended by the FDA for pre-clinical evaluation.
Collapse
Affiliation(s)
- Huaizhong Pan
- Department of Pharmaceutics and Pharmaceutical Chemistry/CCCD, University of Utah, Salt Lake City, Utah 84112, USA
| | | | | | | | | | | |
Collapse
|
14
|
Timchalk C, Kousba AA, Poet TS. An age-dependent physiologically based pharmacokinetic/pharmacodynamic model for the organophosphorus insecticide chlorpyrifos in the preweanling rat. Toxicol Sci 2007; 98:348-65. [PMID: 17504771 DOI: 10.1093/toxsci/kfm119] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Juvenile rats are more susceptible than adults to the acute toxicity of organophosphorus insecticides like chlorpyrifos (CPF). Age- and dose-dependent differences in metabolism may be responsible. Of importance are CYP450 activation and detoxification of CPF to chlorpyrifos-oxon (CPF-oxon) and trichloropyridinol (TCP), as well as B-esterase (B-est) and PON-1 (A-esterase) detoxification of CPF-oxon to TCP. In the current study, a physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) model incorporating age-dependent changes in CYP450, PON-1, and tissue B-est levels for rats was developed. In this model, age was used as a dependent function to estimate body weight which was then used to allometrically scale both metabolism and tissue cholinesterase (ChE) levels. In addition, age-dependent changes in brain, liver, and fat volumes and brain blood flow were obtained from the literature and used in the simulations. Model simulations suggest that preweanling rats are particularly sensitive to CPF toxicity, with levels of CPF-oxon in blood and brain disproportionately increasing, relative to the response in adult rats. This age-dependent nonlinear increase in CPF-oxon concentration may potentially result from both the depletion of nontarget B-est and a lower PON-1 metabolic capacity in younger animals. The PBPK/PD model behaves consistently with the general understanding of CPF toxicity, pharmacokinetics, and tissue ChE inhibition in neonatal and adult rats. Hence, this model represents an important starting point for developing a computational model to assess the neurotoxic potential of environmentally relevant organophosphate exposures in infants and children.
Collapse
Affiliation(s)
- Charles Timchalk
- Battelle Pacific Northwest Division, Center for Biological Monitoring and Modeling, Richland, Washington 99352, USA.
| | | | | |
Collapse
|
15
|
Crow JA, Borazjani A, Potter PM, Ross MK. Hydrolysis of pyrethroids by human and rat tissues: examination of intestinal, liver and serum carboxylesterases. Toxicol Appl Pharmacol 2007; 221:1-12. [PMID: 17442360 PMCID: PMC2692260 DOI: 10.1016/j.taap.2007.03.002] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2007] [Revised: 02/26/2007] [Accepted: 03/02/2007] [Indexed: 11/16/2022]
Abstract
Hydrolytic metabolism of pyrethroid insecticides in humans is one of the major catabolic pathways that clear these compounds from the body. Rodent models are often used to determine the disposition and clearance rates of these esterified compounds. In this study the distribution and activities of esterases that catalyze pyrethroid metabolism have been investigated in vitro using several human and rat tissues, including small intestine, liver and serum. The major esterase in human intestine is carboxylesterase 2 (hCE2). We found that the pyrethroid trans-permethrin is effectively hydrolyzed by a sample of pooled human intestinal microsomes (5 individuals), while deltamethrin and bioresmethrin are not. This result correlates well with the substrate specificity of recombinant hCE2 enzyme. In contrast, a sample of pooled rat intestinal microsomes (5 animals) hydrolyze trans-permethrin 4.5-fold slower than the sample of human intestinal microsomes. Furthermore, it is demonstrated that pooled samples of cytosol from human or rat liver are approximately 2-fold less hydrolytically active (normalized per mg protein) than the corresponding microsomal fraction toward pyrethroid substrates; however, the cytosolic fractions do have significant amounts (approximately 40%) of the total esteratic activity. Moreover, a 6-fold interindividual variation in carboxylesterase 1 protein expression in human hepatic cytosols was observed. Human serum was shown to lack pyrethroid hydrolytic activity, but rat serum has hydrolytic activity that is attributed to a single CE isozyme. We purified the serum CE enzyme to homogeneity to determine its contribution to pyrethroid metabolism in the rat. Both trans-permethrin and bioresmethrin were effectively cleaved by this serum CE, but deltamethrin, esfenvalerate, alpha-cypermethrin and cis-permethrin were slowly hydrolyzed. Lastly, two model lipase enzymes were examined for their ability to hydrolyze pyrethroids. However, no hydrolysis products could be detected. Together, these results demonstrate that extrahepatic esterolytic metabolism of specific pyrethroids may be significant. Moreover, hepatic cytosolic and microsomal hydrolytic metabolism should each be considered during the development of pharmacokinetic models that predict the disposition of pyrethroids and other esterified compounds.
Collapse
Affiliation(s)
- J. Allen Crow
- Center for Environmental Health Sciences, Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, P.O. Box 6100, Mississippi State, MS 39762-6100
| | - Abdolsamad Borazjani
- Center for Environmental Health Sciences, Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, P.O. Box 6100, Mississippi State, MS 39762-6100
| | - Philip M. Potter
- Department of Molecular Pharmacology, St. Jude Children’s Research Hospital, 332 North Lauderdale, Memphis, TN 38105
| | - Matthew K. Ross
- Center for Environmental Health Sciences, Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, P.O. Box 6100, Mississippi State, MS 39762-6100
- Corresponding author: Phone: 662-325-5482, Fax: 662-325-1031,
| |
Collapse
|
16
|
Dolgushin MV, Sosedova LM. Hydrolase and oxidoreductase activities in peripheral blood lymphocytes in combined exposure to biological allergens and sulfur dioxide. Bull Exp Biol Med 2006; 141:257-60. [PMID: 16984112 DOI: 10.1007/s10517-006-0143-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Differences in the metabolic status of peripheral blood lymphocytes were observed after exposure of intact guinea pigs and animals sensitized with biological allergens to sulfur dioxide. When sensitization was complicated by chemical exposure, enzyme activities in lymphocytes depended on the type of allergen and degree of hypersensitivity.
Collapse
Affiliation(s)
- M V Dolgushin
- Angarsk Affiliated Department of Institute of Labor Medicine and Human Ecology, Research Center of Medical Ecology, Siberian Division of Russian Academy of Medical Sciences.
| | | |
Collapse
|
17
|
Abstract
PURPOSE Many topically applied drugs contain esters that are hydrolyzed in the skin. Minipigs have emerged as potential models of human dermatology and, in some aspects, may be superior to commonly used rat skin. The aims of this study were to evaluate the suitability of minipig and rat skin as in vitro models of human epidermal esterase activity. METHODS Naphthyl acetate and para-nitrophenyl acetate were tested as prototypical substrates of carboxylesterases from skin, plasma, and liver. Reaction products were monitored by high-performance liquid chromatography/ultraviolet analysis. RESULTS Hydrolysis efficiency in skin was higher than plasma, but lower than liver. The esterase efficiency of rat skin microsomes (580-1100 min(-1) mg(-1)) was two to three orders of magnitude higher than human (1.3-4.2 min(-1) mg(-1)) and minipig microsomes (1.2-4.2 min(-1) mg(-1)). Rat skin cytosol (80-100 min(-1) mg(-1)) was 2- to 10-fold more efficient than human (2.4-67 min(-1) mg(-1)) or minipig cytosol (18-61 min(-1) mg(-1)). Most importantly, human skin fractions displayed kinetics of hydrolysis very similar to minipig skin. CONCLUSIONS These studies show minipig skin as an appropriate, potentially valuable model for human epidermal ester metabolism and support the use of minipig skin in preclinical development of topically applied compounds.
Collapse
Affiliation(s)
- Jeffery J Prusakiewicz
- Department of Pharmacokinetics, Dynamics and Metabolism, Pfizer Global Research and Development, 2800 Plymouth Rd., Ann Arbor, Michigan 48105, USA.
| | | | | |
Collapse
|
18
|
Anand SS, Kim KB, Padilla S, Muralidhara S, Kim HJ, Fisher JW, Bruckner JV. Ontogeny of hepatic and plasma metabolism of deltamethrin in vitro: role in age-dependent acute neurotoxicity. Drug Metab Dispos 2005; 34:389-97. [PMID: 16326812 DOI: 10.1124/dmd.105.007807] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Deltamethrin (DLM) is a relatively potent and widely used pyrethroid insecticide. Inefficient detoxification has been proposed to be the primary reason for the greater sensitivity of immature rats to the acute neurotoxicity of DLM. The objective of this study was to test this hypothesis by characterizing the age dependence of DLM metabolism in vitro, as well as toxic signs and blood levels of the neurotoxic parent compound following administration of 10 mg DLM/kg p.o. in glycerol formal. Metabolism was quantified in vitro by monitoring the disappearance of the parent compound from plasma [via carboxylesterases (CaEs)] and liver microsomes [via CaEs and cytochromes P450 (P450s)] obtained from 10-, 21-, and 40-day-old male Sprague-Dawley rats. Mean (+/-S.E.) intrinsic clearances (Vmax/Km) in these respective age groups by liver P450s (4.99+/-0.32, 16.99+/-1.85, and 38.45+/-7.03) and by liver CaEs (0.34+/-0.05, 1.77+/-0.38, and 2.53+/-0.19) and plasma CaEs (0.39+/-0.06, 0.80+/-0.09, and 2.28+/-0.56) increased significantly (p<or=0.05) with age, because of progressive increases in Vmax. Intrinsic clearance of DLM by plasma CaEs and liver P450s reached adult levels by 40 days, but clearance by liver CaEs did not. Hepatic P450s played the predominant role in DLM biotransformation in young and adult rats. The incidence and severity of neurotoxic effects varied inversely with age. Correspondingly, blood DLM areas under the concentration versus time curve (AUCs) and Cmax values progressively decreased with increasing age. Internal exposure to DLM (blood AUCs) was closely correlated with toxic signs (salivation and tremors). The present study provides evidence that the limited metabolic capacity of immature rats contributes to elevated systemic exposure and ensuing neurotoxic effects of DLM.
Collapse
Affiliation(s)
- Sathanandam S Anand
- Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, University of Georgia, Athens, GA 30602, USA.
| | | | | | | | | | | | | |
Collapse
|
19
|
Li B, Sedlacek M, Manoharan I, Boopathy R, Duysen EG, Masson P, Lockridge O. Butyrylcholinesterase, paraoxonase, and albumin esterase, but not carboxylesterase, are present in human plasma. Biochem Pharmacol 2005; 70:1673-84. [PMID: 16213467 DOI: 10.1016/j.bcp.2005.09.002] [Citation(s) in RCA: 397] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2005] [Revised: 09/02/2005] [Accepted: 09/07/2005] [Indexed: 11/19/2022]
Abstract
The goal of this work was to identify the esterases in human plasma and to clarify common misconceptions. The method for identifying esterases was nondenaturing gradient gel electrophoresis stained for esterase activity. We report that human plasma contains four esterases: butyrylcholinesterase (EC 3.1.1.8), paraoxonase (EC 3.1.8.1), acetylcholinesterase (EC 3.1.1.7), and albumin. Butyrylcholinesterase (BChE), paraoxonase (PON1), and albumin are in high enough concentrations to contribute significantly to ester hydrolysis. However, only trace amounts of acetylcholinesterase (AChE) are present. Monomeric AChE is seen in wild-type as well as in silent BChE plasma. Albumin has esterase activity with alpha- and beta-naphthylacetate as well as with p-nitrophenyl acetate. Misconception #1 is that human plasma contains carboxylesterase. We demonstrate that human plasma contains no carboxylesterase (EC 3.1.1.1), in contrast to mouse, rat, rabbit, horse, cat, and tiger that have high amounts of plasma carboxylesterase. Misconception #2 is that lab animals have BChE but no AChE in their plasma. We demonstrate that mice, unlike humans, have substantial amounts of soluble AChE as well as BChE in their plasma. Plasma from AChE and BChE knockout mice allowed identification of AChE and BChE bands without the use of inhibitors. Human BChE is irreversibly inhibited by diisopropylfluorophosphate, echothiophate, and paraoxon, but mouse BChE spontaneously reactivates. Since human plasma contains no carboxylesterase, only BChE, PON1, and albumin esterases need to be considered when evaluating hydrolysis of an ester drug in human plasma.
Collapse
Affiliation(s)
- Bin Li
- University of Nebraska Medical Center, Eppley Institute, Omaha, NE 68198-6805, USA
| | | | | | | | | | | | | |
Collapse
|
20
|
Antonijević B, Bokonjić D, Stojiljković MP, Kilibarda V, Milovanović ZA, Nedeljković M, Maksimović M. Efficacy of Trimedoxime in Mice Poisoned with Dichlorvos, Heptenophos or Monocrotophos. Basic Clin Pharmacol Toxicol 2005; 96:111-7. [PMID: 15679473 DOI: 10.1111/j.1742-7843.2005.pto960204.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The aim of the study was to examine antidotal potency of trimedoxime in mice poisoned with three direct dimethoxy-substituted organophosphorus inhibitors. In order to assess the protective efficacy of trimedoxime against dichlorvos, heptenophos or monocrotophos, median effective doses and efficacy half-times were calculated. Trimedoxime (24 mg/kg intravenously) was injected 5 min. before 1.3 LD50 intravenously of poisons. Activities of brain, diaphragmal and erythrocyte acetylcholinesterase, as well as of plasma carboxylesterases were determined at different time intervals (10, 40 and 60 min.) after administration of the antidotes. Protective effect of trimedoxime decreased according to the following order: monocrotophos > heptenophos > dichlorvos. Administration of the oxime produced a significant reactivation of central and peripheral acetylcholinesterase inhibited with dichlorvos and heptenophos, with the exception of erythrocyte acetylcholinesterase inhibited by heptenophos. Surprisingly, trimedoxime did not induce reactivation of monocrotophos-inhibited acetylcholinesterase in any of the tissues tested. These organophosphorus compounds produced a significant inhibition of plasma carboxylesterase activity, while administration of trimedoxime led to regeneration of the enzyme activity. The same dose of trimedoxime assured survival of experimental animals poisoned by all three organophosphorus compounds, although the biochemical findings were quite different.
Collapse
Affiliation(s)
- Biljana Antonijević
- Institute of Toxicological Chemistry, School of Pharmacy, University of Belgrade, Vojvode Stepe 450, Serbia and Montenegro.
| | | | | | | | | | | | | |
Collapse
|
21
|
Abstract
B-esterases are serine hydrolases composed of cholinesterases, including acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), and carboxylesterase (CbE). These esterases, found in blood plasma, are inhibited by organophosphorus (OP) and carbamate (CB) insecticides and can be used as nondestructive biomarkers of exposure to anticholinesterase insecticides. Furthermore, B-esterases are involved in detoxification of these insecticides. In order to establish the level of these enzymes and to have reference values for their normal activities, total plasma cholinesterase (ChE), AChE and BChE activities, and plasma CbE activity were determined in 729 European raptors representing 20 species, four families, and two orders. The diurnal families of the Falconiforme order were represented by Accipitridae and Falconidae and the nocturnal families of the Strigiforme order by Tytonidae and Strigidae. Intraspecies differences in cholinesterase activities according to sex and/or age were investigated in buzzards (Buteo buteo), sparrowhawks (Accipiter nisus), kestrels (Falco tinnunculus), barn owls (Tyto alba), and tawny owls (Strix aluco). Sex-related differences affecting ChE and AChE activities were observed in young kestrels (2-3-mo-old) and age-related differences in kestrels (ChE and AChE), sparrowhawks (AChE), and tawny owls (ChE, AChE, and BChE). The interspecies analysis yielded a negative correlation between ChE activity and body mass taking into account the relative contribution of AChE and BChE to ChE activity, with the exception of the honey buzzard (Pernis apivorus). The lowest ChE activities were found in the two largest species, Bonelli's eagle (Hieraaetus fasciatus) and Egyptian vulture (Neophron percnopterus) belonging to the Accipitridae family. The highest ChE activities were found in the relatively small species belonging to the Tytonidae and Strigidae families and in honey buzzard of the Accipitridae family. Species of the Accipitridae, Tytonidae, and Strigidae families were characterized by a BChE contribution that dominated the total ChE activity, while in the species of the Falconidae family, AChE activity dominated. With the exception of the barn owl, CbE activity (eserine-insensitive alpha-naphthyl acetate esterase [alpha-NAE] activity) in all species was almost absent or very low. The values obtained in this study for ChE, AChE, and BChE activities and the AChE:BChE ratios for buzzard, kestrel, barn owl, and tawny owl provide a good estimate of the normal values in free-living individuals of these European species. They can be used as a baseline to evaluate the effect of anticholinesterase insecticides in the field.
Collapse
Affiliation(s)
- Claudie Roy
- Unitéde Phytopharmacie et Médiateurs chimiques, Institut National de la Recherche Agronomique (INRA), Route de Saint-Cyr, 78026 Versailles Cedex, France.
| | | | | | | |
Collapse
|
22
|
Karanth S, Liu J, Olivier K, Pope C. Interactive toxicity of the organophosphorus insecticides chlorpyrifos and methyl parathion in adult rats. Toxicol Appl Pharmacol 2004; 196:183-90. [PMID: 15081265 DOI: 10.1016/j.taap.2003.12.014] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2003] [Accepted: 12/10/2003] [Indexed: 10/26/2022]
Abstract
The acute interactive toxicity following exposure to two common organophosphorus (OP) insecticides, chlorpyrifos (CPF) and methyl parathion (MPS), was investigated in adult male rats. Oral LD1 values were estimated by dose-response studies (CPF = 80 mg/kg; MPS = 4 mg/kg, in peanut oil, 1 ml/kg). Rats were treated with both toxicants (0.5 or 1 x LD1) either concurrently or sequentially, with 4-h intervals between dosing. Functional signs of toxicity (1-96 h) and cumulative lethality (96 h) were recorded. Rats treated with CPF (1 x LD1) did not show any signs of toxicity although MPS (1 x LD1) elicited slight to moderate signs (involuntary movements) within 1-2 h. Concurrent exposure (LD1 dosages of both CPF and MPS) caused slight signs of toxicity only apparent between 24 and 48 h after dosing. When rats were treated sequentially with MPS first followed by CPF 4 h later, slight signs of toxicity were noted between 6 and 24 h, whereas reversing the sequence resulted in 100% lethality within 1 h of the second dosage. Following exposure to lower dosages (0.5 x LD1), the CPF first group showed higher signs of cholinergic toxicity compared with MPS first or concurrent groups. Cholinesterase inhibition in plasma, diaphragm, and frontal cortex was generally higher in rats treated sequentially with CPF first than in those treated initially with MPS from 4 to 24 h after dosing. Plasma and liver carboxylesterase inhibition at 4 h was also significantly higher in the CPF first (62-90%) compared with MPS first (22-43%) group, while at 8 and 24 h, there was no significant difference between any of the treatment groups. ChE inhibition assays to evaluate in vitro hepatic detoxification of oxons indicated that carboxylesterase (CE)- and A-esterase-mediated pathways are markedly less important for methyl paraoxon (MPO) than chlorpyrifos oxon (CPO) detoxification. CPF pretreatment blocked hepatic detoxification of methyl paraoxon while MPS pretreatment had minimal effect on hepatic CPO detoxification ex vivo. These findings suggest that the sequence of exposure to two insecticides that elicit toxicity through a common mechanism can markedly influence the cumulative action at the target site (acetylcholinesterase, AChE) and consequent functional toxicity.
Collapse
Affiliation(s)
- Subramanya Karanth
- Department of Physiological Sciences, College of Veterinary Medicine, Oklahoma State University, Stillwater, OK 74078, USA
| | | | | | | |
Collapse
|
23
|
Weiden PL, Giblett ER, Anderson JE, Storb R. Esterase D: polymorphic red blood cell enzyme in the dog. Transplantation 1980; 30:230-1. [PMID: 14582183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023]
Affiliation(s)
- P L Weiden
- Fred Hutchinson Cancer Research Center, Division of Oncology, 1124 Columbia Street, Seattle, Washington 98104, USA
| | | | | | | |
Collapse
|