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At least 19 recordsLinked to original sources
PubMed1992

Cimetidine-carbaryl interaction in humans: evidence for an active metabolite of carbaryl.

The influence of cimetidine on the pharmacokinetic and pharmacodynamic response to the insecticide carbaryl has been investigated in isolated human erythrocytes (red blood cells; RBC) and after oral administration of 1 mg/kg carbaryl to four normal subjects in the absence or presence of cimetidine (300 mg, 8/hr for 3 days). Carbaryl induced a concentration-dependent reduction of isolated RBC acetylcholinesterase activity requiring 1 microgram/ml to achieve 20% inhibition. Cimetidine also induced a dose-dependent inhibition of RBC acetylcholinesterase activity, but at 40-fold higher concentrations. At high concentrations, cimetidine was additive to carbaryl-induced inhibition of RBC acetylcholinesterase, but exhibited no effect at the therapeutically relevant concentrations (10 micrograms/ml). After oral carbaryl administration to normal subjects, plasma concentrations rapidly rose to a peak, then declined with a half-life of 0.79 +/- 0.47 hr. Oral carbaryl clearance was 5.4 +/- 2.0 l/min. Peak plasma carbaryl concentrations were associated with 27% inhibition of RBC acetylcholinesterase activity, and the concentration associated with a reduction of RBC acetylcholinesterase activity of 20% was 0.02 microgram/ml. The terminal half-life for the dynamic response was 2.6 +/- 1.5 hr. After pretreatment with cimetidine, peak plasma carbaryl concentrations doubled and clearance was reduced (to 2.5 +/- 1.5 l/min) (P less than .05). However, half-life remained unchanged. Despite increased carbaryl levels, the maximum inhibition of RBC acetylcholinesterase activity was significantly reduced, and the concentration of carbaryl required to achieve 20% inhibition of RBC acetylcholinesterase activity was increased to approximately 0.5 microgram/ml. These results are consistent with the hypothesis that carbaryl is metabolized by drug-metabolizing enzymes that can be inhibited by cimetidine.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholinesterase↗
PubMed1991

Hydrolysis of carbaryl by a Pseudomonas sp. and construction of a microbial consortium that completely metabolizes carbaryl.

Two Pseudomonas spp. (isolates 50552 and 50581) isolated from soil degraded 1-naphthol and carbaryl, an N-methylcarbamate pesticide, respectively. They utilized these compounds as a sole source of carbon. 1-Naphthol was completely metabolized to CO2 by the isolate 50552, while the carbaryl was first hydrolyzed to 1-naphthol and then converted into a brown-colored compound by the isolate 50581. The colored metabolite was not degraded, but 1-naphthol produced by the isolate 50581 during the exponential phase of growth was metabolized by the isolate 50552. The two isolates were used to construct a bacterial consortium which completely catabolized carbaryl to CO2. No metabolite was detected in the cell cultures of the consortium. The isolate 50581 harbored a 50-kb plasmid pCD1, while no plasmid was detected in the isolate 50552. The isolated bacteria individually or as a consortium may be used for detoxification of certain industrial and agricultural wastes.

Biodegradation, Environmental↗
PubMed1986

Pentylenetetrazol: effect on carbaryl-induced changes of serotonin metabolism in pons-medulla of rat brain.

Oral administration of carbaryl to adult male albino rats produced a dose dependent increase in the steady state level of 5-hydroxytryptamine (5-HT) at 1.00 h in pons-medulla (PM). 5-Hydroxyindole acetic acid (5-HIAA) concentration was significantly elevated only in response to a higher dose of this pesticide under similar conditions. A time course study with carbaryl and pentylenetetrazol (PTZ) showed a characteristic elevation of the steady state level of 5-HT in PM, but the 5-HIAA level was significantly elevated at 0.5 h only after carbaryl treatment. No significant change of the 5-HIAA level was evident after administration of PTZ alone or in combination with carbaryl. Tryptophan concentration was significantly elevated in PM at 0.5 h after carbaryl treatment and at 1.0 h after carbaryl + PTZ treatment. No significant change of tryptophan concentration was evident after the administration of PTZ alone under similar conditions. Measurement of (1) pargyline induced (a) accumulation of 5-HT and (b) depletion of 5-HIAA levels, and (2) probenecid-induced accumulation of 5-HIAA level in presence and absence of carbaryl and revealed that carbaryl accelerated the synthesis as well as the breakdown of 5-HT, whereas PTZ alone or in combination with carbaryl accelerated the synthesis of 5-HT without affecting its catabolism. The potency of this pesticide in elevating the pargyline-induced accumulation of 5-HT is in the order of carbaryl + PTZ greater than PTZ congruent to carbaryl. These results suggest that the carbaryl-induced increase in the synthesis of 5-HT is potentiated, and the turnover is reduced, in PM when PTZ is administered to the carbaryl-intoxicated rats.

Animals↗
PubMed1989

Effect of carbaryl on the respiration, glycolysis and gluconeogenesis in isolated liver cells.

The effects of 1-naphthyl-N-methylcarbamate (carbaryl) upon respiration, glycolysis and gluconeogenesis in isolated rat hepatocytes was studied. The carbaryl at 0.01; 0.1 and 1.0 mM were dissolved in 1% dimethylsulphoxide. Concentrations of carbaryl at 1.0 mM reduces oxygen consumption. The decrease in the metabolic production of CO2 is significant at even the lowest of the concentrations. The utilization of glucose and the endogenous production of lactic is unaffected by treatment with carbaryl. The net glycolytic flux is decreased. On the other hand, the carbaryl inhibits lactate-gluconeogenesis at all concentrations of substrate studied. Gluconeogenesis from fructose or pyruvate or alanine is also inhibited by carbaryl 1 mM. Carbaryl decreases the lactic dehydrogenase activity but this diminution is only significant for the greatest concentration assayed. The activity of glucose-6-phosphatase is enhanced by carbaryl, but the increase is only significant for 1 mM carbaryl. The glutamic-oxalacetic transferase cytoplasmic and mitochondrial activities are inhibited by 0.1 mM and 1.0 mM carbaryl. Carbaryl decreases glucose production by hepatic cells, and suggests that the carbaryl-induced hyperglycemia in the fasted animal would be due to deficiencies in the peripheral utilization of the glucose.

Animals↗
PubMed1980

Excretion and disposition of [14C]carbaryl in pregnant, non-pregnant and foetal tissues of the rat after acute administration.

1. Non-pregnant or pregnant Sprague-Dawley rats on the 18th and 19th days of gestation were injected i.p. with a tracter dose (2.8 microCi/kg) of either [ring-14C]carbaryl or [carbonyl-14C]carbaryl. Distribution of total 14C was examined in foetal, maternal and non-pregnant rat tissues. Pregnancy alters the disposition and excretion of carbaryl. 2. Carbaryl crossed the placenta and was rapidly distributed in all foetal tissues. Highest concentrations were seen in foetal kidney. At 8 h after injection, foetal brain, heart and lung all contained more 14C, on a weight basis, than their maternal organ counterparts. Elimination from the whole foetus was biphasic, and after 8 h approx. 3% of the dose was still present in the whole foetus. 3. Significantly more 14CO2 was exhaled by the pregnant rat during 8 h than by non-pregnant. Urinary excretion of 14C after dosage with [ring-14C]carbaryl was significantly less in pregnant than in non-pregnant rats. 4. Kinetically, the tissue distribution of 14C from carbaryl or metabolites was biphasic in pregnant and non-pregnant animals. [14C]carbaryl concn. declined rapidly for 1 to 2 h. After 2 h the 14C levels from animals dosed with [ring-14C]carbaryl declined more slowly. 5. The pattern of 14C distribution was more complicated after injection of [carbonyl-14C]carbaryl. The 14C activity increased in the animal tissues after 2 h, in contrast to animals dosed with [ring-14C]carbaryl. Non-pregnant animals treated with [carbonyl-14C]carbaryl did not show a similar pattern of distribution. Carbamylated tissue proteins may, after time, release some bound carbonyl-14C label, causing the increase in 14C activity seen between 2 and 8 h. However, this does not necessarily imply uptake of the intact carbamate.

Animals↗
PubMed1983

Evaluation of cellular and humoral mechanisms of carbaryl-induced reticuloendothelial phagocytic depression.

The simultaneous injection of carbaryl and colloidal carbon phagocytized by the reticuloendothelial cells results in competition between the two substances in favor of the carbon particles. Experiments with opsonized carbaryl suggest that the decrease in carbaryl blood clearance by the colloid is mediated by a depletion of serum opsonins. Following blockade, the liver carbaryl uptake was depressed in the control group (17%), while it was increased in the opsonized group (12%). With all preparations of carbaryl, opsonized or non-opsonized, colloidal carbon produced a slight and variable increase in carbaryl uptake by the spleen and lungs. These results indicate that, besides the uptake of carbaryl by the hepatocytes, other clearance sites must also be considered such as the Kupffer cells and other liver sinusoidal cells. Moreover our results show that intravenous administration of carbaryl induces a state of phagocytic depression as indicated by impaired intravascular phagocytosis and depressed hepatic uptake of the reticuloendothelial (RE)-test colloidal suspension. The results obtained from injection of opsonized colloidal particles during carbaryl-induced RE-depression, and the fact that carbaryl and carbon are both opsonized by the same serum factor, suggest that the mechanisms of RE-blockade involve selective hepatic and splenic macrophage failure and depletion of serum opsonins. According to our enzymatic investigation, this failure of the RE system to incorporate colloids during carbaryl--RE-blockade could be due to a defect in the activity of macrophage membrane-bound serine esterase.

Animals↗
PubMed1982

Exposure of urban applicators to carbaryl.

Thirty-eight urban volunteers from the Lincoln and Omaha, Nebraska areas were monitored for carbaryl exposure during the summer of 1979. All volunteers were involved in the application of carbaryl incidental to their employment or leisure activities. The investigators made no attempt to affect the method of carbaryl application. The mean rates of carbaryl exposure were 3.85 and 0.26 microgram cm-2 hr-1, respectively, for the outside of the clothing and the skin beneath the clothing; clothing apparently provided an effective barrier to carbaryl penetration. The rate of carbaryl exposure to the hands of applicators was 2.36 and 24.96 micrograms cm-21 hr-1, respectively, for applicators with and without gloves. The maximum dermal exposure recorded in this study was 2.86 mg kg-1 hr-1 which is significantly less than the stimated dermal LD50 value for carbaryl (4000 mg kg-1). The maximum air concentration of carbaryl was 0.28 microgram L-1. Only a small mean decrease was found in the applicators serum (-1.01%) or erythrocyte (-1.39%) acetylcholinesterase activity. Although some applicators had decreases in either serum or erythrocyte acetylcholinesterase activity greater than 20%, an equal number had increases of the same magnitude. The mean total carbaryl exposure to the applicators, expressed as a percent of toxic dose per hr, was 0.01%, with a maximum estimated exposure of 0.08%.

Acetylcholinesterase↗
PubMed1976

Identification by physical means of organic moieties of conjugates produced from carbaryl by tobacco cells in suspension culture.

Carbaryl (1-naphthyl methylcarbamate), labeled with 14C in the C1-naphthyl, carbonyl, or N-methyl position, was introduced into the culture medium of tobacco cells in suspension culture. Following incubation, cells were homogenized in water, centrifugated, and supernatants hydrolyzed with beta-glucosidase or HCl. Organic moieties (moieties) were characterized by two-dimensional thin-layer chromatography (TLC), and many were subsequently identified by infrared and mass spectrometry. On the basis of the data obtained with 14C1-naphthyl-labeled carbaryl, it appeared that 18.4% of the total characterized metabolites represented unconjugated N-CH2OH- carbaryl [1-naphthyl N-(hydroxymethyl)carbamate], excreted by the cells into the culture medium. The metabolites found in the cells primarily consisted of conjugates of 1-naphthol (73.6% of the total characterized metabolites) and N-CH2OH-carbaryl (2.5%). Conjugates of 7-hydroxycarbaryl (7-hydroxy-1-napthyl methylcarbamate), 4-hydroxycarbaryl (4-hydroxy-1-naphthyl methylcarbamate), and 5-hydroxycarbaryl (5-hydroxy-1-naphthyl methylcarbamate) were also detected in small amounts. Of five unknown 14C1-naphthyl-labeled carbaryl metabolites, three were tentatively characterized as: O-1-naphthylcholesterol (Cholest-5-en-3beta-yl-1-napthol: 3.0%); an unconjugated hydroxylated 1,4-dihydro-1,4-epiperoxynapththalene (1.4%); and an acidlabile, beta-glucosidase-resistant conjugate of a cis-dihydrodiol of 1-naphthol (0.3%; other than the trans-5,6-dihydrodiol). The cholesterol derivative may represent a new "detoxification mechanism" in plants; the epiperoxide may help to elucidate plant oxidation mechanisms. A new TLC procedure was developed which successfully separated the acetate derivative of N-hydroxycarbaryl (1-naphthyl N-hydroxy-N-methylcarbamate) from 12 other common moieties of carbaryl metabolites and their acetate derivatives. A new two-dimensional TLC system was developed for the separation of underivatized N-hydroxycarbaryl from 14 other moieties of carbaryl metabolites; two additional two-dimensional TLC systems were utilized for moiety separations. With these TLC procedures, no conjugated or unconjugated N-hydroxycarbaryl could be detected in any tobacco cell culture fraction after incubation of cells in medium containing radiolabeled carbaryl. Authentic 14C1-naphthyl-labeled N-CH2OH-carbaryl was shown to be converted to desmethylcarbaryl (1-naphthylcarbamate) 97%) and 1-naphthol (3%) by 0.1N HCl hydrolysis.

Carbaryl↗
PubMed1985

Effect of pentylenetetrazol on carbaryl-induced changes in striatal catecholamines.

Administration of pentylenetetrazol (PTZ) (60 mg/kg, s.c.) to normal or carbaryl (200 mg/kg, p.o.) treated adult male albino rats produced characteristic changes in the steady-state levels of striatal dopamine (DA), noradrenaline (NA) and homovanillic acid (HVA) at different time intervals (0.5, 1.0 and 2.0 hr). The elevation of striatal NA level was found to be more pronounced with PTZ than that produced by carbaryl. Treatment of rats with PTZ alone caused a significant elevation of DA levels only at 2.0 hr without any significant change in the level of HVA at any time interval. Carbaryl which did not have any significant effect on striatal DA level produced an elevation of HVA at 0.5 hr and 1.0 hr in striatum. The simultaneous administration of PTZ and carbaryl, under similar conditions, caused a marked reduction in the level of NA at 0.5 hr and DA at 1.0 hr without any significant effect on (i) both the amine levels at 2.0 hr and (ii) HVA level at any of the time intervals. Measurement of (a) alpha-methyl-p-tyrosine (alpha-MpT) (250 mg/kg, i.p.) induced depletion of striatal DA and NA, (b) FLA-63 (25 mg/kg, i.p.) induced disappearance of NA, (c) pargyline (75 mg/kg, i.p.) induced reduction and probenecid (200 mg/kg, i.p.) induced accumulation of striatal HVA in the presence or absence of PTZ and/or carbaryl revealed that: (1) PTZ or carbaryl alone caused a significant increase in the turnover of striatal DA; (2) the turnover of striatal NA was significantly increased after PTZ treatment but not after carbaryl administration; (3) the simultaneous administration of carbaryl and PTZ, on the other hand, attenuated (a) PTZ- or carbaryl-induced increase in metabolic activity of the striatal dopaminergic system, and (b) the enhanced anabolic activity of striatal noradrenergic system caused by PTZ, but failed to affect the enhanced utilization of striatal NA induced by PTZ alone.

Animals↗
PubMed1990

Interaction of central serotonin and dopamine in the regulation of carbaryl-induced tremor.

Carbaryl (50-200 mg/kg, p.o.) produced dose-dependent tremors and inhibition of striatal AChE activity. A dose-dependent elevation of striatal 5-HT and 5-HIAA levels was also observed with carbaryl but at the higher doses (100-200 mg/kg p.o.). L-Trp or 5-HTP or haloperidol potentiated the carbaryl-induced tremors. Further, 5-HTP or haloperidol, when administered (i) alone, reduced the ED50 value and increased the duration of carbaryl-induced tremors without affecting the maximum tremorogenic response of rats and (ii) together, did not change any of these measures significantly. Atropine (acetylcholine antagonist) completely blocked the tremors produced by carbaryl in the absence or presence of 5-HTP or haloperidol. Methysergide (5-HT antagonist) and bromocriptine (DA agonist) antagonised the potentiating effect of 5-HTP and haloperidol, respectively, on the carbaryl-induced tremors. Furthermore, bromocriptine antagonised the potentiating effect of 5-HTP on the carbaryl-induced tremor but, methysergide failed to achieve this antagonism in presence of haloperidol. These results indicate that carbaryl-induced tremors primarily involve the activation of central cholinoceptors and that the serotonergic potentiation of carbaryl-induced tremors is possibly mediated through the dopaminergic disinhibition of cholinergic neurons.

5-Hydroxytryptophan↗
PubMed1984

The interaction of carbaryl with the metabolism of isolated hepatocytes: I. Effect on respiration and glycolysis.

The in vitro interaction of the insecticide 1-naphthyl-N-methylcarbamate (carbaryl) with respiration and the glycolytic pathway was studied in hepatocytes isolated according to a modified version of the method of Berry and Friend. The cells were subjected to concentrations of carbaryl at 0.01, 0.1 and 1.0 mM dissolved in 1% dimethylsulphoxide. The results show that dimethylsulphoxide induces a slight stimulation of the respiratory coefficients. Concentrations of carbaryl at 0.01 and 0.1 mM did not significantly modify oxygen consumption, but at 1.0 mM this was reduced by 40% in relation to the dimethylsulphoxide-treated group. On the other hand, the decrease in the metabolic production of CO2 is significant at even the lowest of the concentrations with resultant major changes in the respiratory quotient. The utilization of glucose is unchanged by treatment with carbaryl. The endogeneous production of lactic acid is unaffected by the presence of the exogenous agents studied. The net metabolic production of lactate was strongly inhibited by dimethylsulphoxide and further inhibited by increasing concentrations of carbaryl. 1 mM of carbaryl completely blocks the net glycolytic flux. The results indicate that carbaryl produces major changes at the glycolytic pathway of hepatic cells. But this result may be understood not as an effect due to carbaryl per se, but as the role of other factors such as dimethylsulphoxide or metabolites of nonenzymatic hydrolysis or carbaryl which also would be involved.

Animals↗
PubMed1984

The interaction of carbaryl with the metabolism of isolated hepatocytes: II. Effect on gluconeogenesis.

The effects of 1-naphthyl-N-methylcarbamate (carbaryl) upon glucose production from several precursors (lactate, glycerol, alanine, fructose and pyruvate) and on activities of gluconeogenic enzymes (glucose-6-phosphatase, lactate dehydrogenase and aspartate aminotransferase) in isolated rat hepatocytes was studied. The results show that carbaryl inhibits lactate-gluconeogenesis at all concentrations of substrate studied. Gluconeogenesis from 10 mM fructose or 10 mM pyruvate or 10 mM alanine is also inhibited by carbaryl 1 mM. However, glycerol-gluconeogenesis is unaffected. Concentrations of carbaryl at 0.01 and 0.1 mM did not significantly modify lactic dehydrogenase activity, but at 1.0 mM this activity was reduced by 38% in relation to the dimethylsulphoxide-treated group. The synthetic activity of glucose-6-phosphatase is enhanced by carbaryl, but the increase is only significant for 1 mM carbaryl. In the study of aspartate aminotransferase activities two fractions, cytoplasmic and mitochondrial, are differentiated; and, it is observed that both fractions are inhibited by 0.1 and 1.0 mM carbaryl. The results indicate that carbaryl produces major decreases of the glucose production by hepatic cells, and suggest that the carbaryl-induced hyperglycemia in the fasted animal would be due to deficiencies in the peripheral utilization of the glucose.

Animals↗
PubMed1998

Carbaryl, a carbamate insecticide, is a ligand for the hepatic Ah (dioxin) receptor.

The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that mediates many of the biological and toxicological actions of a variety of hydrophobic natural and synthetic chemicals, including the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin). Induction of CYP1A1 gene expression is one such response that is known to be regulated by the AhR complex. It was recently reported (Ledirac et al., Toxicol. Appl. Pharmacol. 144, 177-182, 1997) that, although carbaryl, a carbamate insecticide, can induce AhR-dependent expression of CYP1A1, it was not an AhR ligand. Since this apparent ligand-independent activation of the AhR is difficult to reconcile given what is known about the mechanism of AhR action, we have examined the ability of carbaryl to stimulate the AhR signaling pathway. Not only was dioxin responsive element-driven luciferase gene expression induced by carbaryl in stably transfected mouse, rat, guinea pig, and human cells, gel retardation analysis revealed that carbaryl stimulated AhR transformation and DNA binding in vitro and in cells in culture. Dose-response experiments revealed that carbaryl was 300,000-fold less potent that the prototypical inducer, TCDD, in both inducing luciferase gene expression and stimulating AhR transformation and DNA binding in vitro, suggesting that carbaryl itself was the inducing agent. The identification of carbaryl as an AhR ligand was demonstrated by its ability to competitively inhibit [3H]-TCDD to the guinea pig hepatic cytosolic AhR. Our results confirm that carbaryl is both a weak AhR ligand and inducer of AhR-dependent gene expression and argue against its proposed ligand-independent mechanism of AhR activation.

Animals↗