Aging and Spontaneous Reactivation of Human Plasma Cholinesterase Activity After Inhibition by Organophosphorus Pesticides

1993 ◽  
Vol 12 (6) ◽  
pp. 497-503 ◽  
Author(s):  
H.J. Mason ◽  
E. Waine ◽  
A. Stevenson ◽  
H.K. Wilson
Keyword(s):  
Enzyme Activity ◽  
Human Plasma ◽  
Ex Vivo ◽  
Organophosphorus Pesticides ◽  
Plasma Cholinesterase ◽  
Phosphoryl Group ◽  
Human Plasma Cholinesterase ◽  
Spontaneous Reactivation

The in vitro rates of aging and spontaneous reactivation of human plasma cholinesterase (ChE) after inhibition by several organophosphorus pesticides (OPs) have been studied. After inhibition by OP the enzyme can undergo two simultaneous reactions; spontaneous reactivation to the active enzyme and 'aging' to an irreversibly inhibited form of the enzyme. The rates of these two reactions depend on the nature of the phosphoryl group of the OP bound to the active site of ChE. Most OPs registered for use in the UK have dimethoxy or diethoxy groups attached to the phosphorus atom. Reaction rate constants for aging and spontaneous reactivation are reported. Dimethoxy OPs cause half-lives of aging in human plasma ChE of approximately 6 hours and 23 hours at 37°C and 22°C respectively; for diethoxy OPs the values are 12 hours and 39 hours. Reappearance of enzyme activity, after removal of OP, reduced any inhibition by a maximum of 25% for dimethoxy OPs; this reappearance of enzyme activity occurs with a 'half-life' of 5 hours and 15 hours at 37°C and 22°C. These effects, both in vivo and ex vivo, may have relevance in developing a monitoring strategy for dimethoxy OPs using plasma ChE measurements. Inhibition by diethoxy OPs spontaneously reactivates very slowly, even at 37°C, and would not practically influence the measured inhibition. No spontaneous reactivation was detected in human plasma ChE inhibited by the methoxy-ethylamino substituted OP (propetamphos) or the methoxy-methylamino substituted OP (crufomate) during 45 hours incubation at 37°C.

THE EFFECT IN VITRO OF THYROXINE, GLUCAGON, THYROTROPHIN AND ANTITHYROID DRUGS ON 'USUAL' AND 'ATYPICAL' HUMAN PLASMA CHOLINESTERASE

1970 ◽  
Vol 47 (2) ◽  
pp. 177-182 ◽  
Author(s):  
MARY WHITTAKER
Keyword(s):  
Human Plasma ◽  
Plasma Cholinesterase ◽  
Thyroid Stimulating Hormone ◽  
Antithyroid Drugs ◽  
Human Plasma Cholinesterase ◽  
Stimulating Hormone

SMUMARY Concentrations of thyroxine above 10-7m inhibited the activity of the 'usual' and 'atypical' human plasma cholinesterase in vitro. The 'atypical' enzy mewas more readily inhibited and the ratio of the I50 atypical: I50 usual indicates that the hormone can be used as a differential inhibitor to identify the two phenotypes. Similar results were obtained with thiourea, but the action of thiouracil appeared to differ in so far as this inhibited both enzymes to the same extent. Neither glucagon nor thyroid stimulating hormone had any effect.

A new succinylcholine-based assay of plasma cholinesterase.

1984 ◽  
Vol 30 (2) ◽  
pp. 192-195 ◽  
Author(s):  
M H Abernethy ◽  
P M George ◽  
V E Melton
Keyword(s):  
Hydrogen Peroxide ◽  
Enzyme Activity ◽  
Plasma Cholinesterase ◽  
Choline Oxidase ◽  
Rate Of Hydrolysis ◽  
The Mean ◽  
Variant Enzyme ◽  
Hydrolysis Of

Abstract We describe a new method for measuring the in vitro rate of hydrolysis of the muscle relaxant succinylcholine. This substrate is hydrolyzed by plasma cholinesterase (EC 3.1.1.8). The resulting choline is determined by measuring the hydrogen peroxide formed on its oxidation by choline oxidase (EC 1.1.3.17). This is done by use of phenol and aminoantipyrine coupled to peroxidase, and yields an intense chromophore, Amax 500 nm. The assay requires 0.1 mL of plasma, and is precise and specific. The CV was 2.7% within run, 7.3% between run. For the usual (U variant) enzyme the Km is 53 mumol/L. Enzyme activity is removed by anticholinesterase antiserum, and is inhibited by dibucaine with a Ki of 2 mumol/L. Ten samples can be assayed in duplicate in an hour. This method is suited to routine use in any laboratory that has a simple spectrophotometer. The mean activity in 11 individuals with the cholinesterase phenotype UU was 105 U/L, for seven UA heterozygotes 61 U/L, and for three AA homozygotes 4 U/L. To the extent allowed by extrapolation from in vitro to in vivo results, this method should increase diagnostic accuracy and may directly predict duration of succinylcholine-induced apnea.

Rates of spontaneous reactivation and aging of acetyicholinesterase in human erythrocytes after inhibition by organophosphorus pesticides

2000 ◽  
Vol 19 (9) ◽  
pp. 511-516 ◽  
Author(s):  
H J Mason ◽  
C Sams ◽  
A J Stevenson ◽  
R Rawbone
Keyword(s):  
Blood Sample ◽  
Ex Vivo ◽  
Organophosphorus Pesticides ◽  
General Structure ◽  
Plasma Cholinesterase ◽  
Acetylcholinesterase Inhibition ◽  
Red Cell ◽  
Plasma Enzyme ◽  
Cell Enzyme ◽  
Spontaneous Reactivation

The in vitro rates of spontaneous reactivation and aging in human erythrocyte acetylcholinesterase were studied after inhibition by a dimethoxy (RjR2) and diethoxy substituted (RjR2) organophosphate pesticide (OP) of general structure R1R2P(O)X. These have been compared with data for human plasma cholinesterase previously reported using a similar methodology. A significantly slower rate of aging for erythrocyte acetylcholinesterase was found compared to plasma cholinesterase, whether inhibited by dimethoxy or diethoxy substituted OPs. For diethoxy OPs the rate of spontaneous reactivation of the inhibited plasma enzyme was significantly slower than for the inhibited red cell enzyme. This acetylcholinesterase, and previously published plasma cholinesterase, data suggest that in practise a blood sample taken 30-40 h after significant acute OP exposure will still show inhibition in either plasma or erythrocyte cholinesterase when analysed, but that any inhibited plasma enzyme is more likely to be in the aged form. In contrast a substantial proportion of the erythrocyte acetylcholinesterase is found unaged and therefore sensitive to reactivation by oximes. Samples from an occupational exposure where depressions in plasma or erythrocyte cholinesterase activity from baseline measurements were reactivated ex vivo using the oxime 2-PAM support this hypothesis. These data also confirm that the plasma enzyme is a more sensitive than erythrocyte acetylcholinesterase as an indicator of OP exposure and thus the potential value of ex vivo oxime reactivation of erythrocyte acetylcholinesterase in a blood sample to indicate subclinical OP exposure may be limited. However, this study is too small to draw conclusions on the sensitivity of ex vivo oxime reactivation of acetylcholinesterase as a novel biomarker of excessive OP absorption. Given that there is a better relationship between anticholinergic symptoms and red cell acetylcholinesterase inhibition, and that the slower resynthesis rate of any aged or inhibited red cell enzyme may be interpretatively useful when venepuncture is delayed, it is suggested that red cell acetylcholinesterase activity does have a place in monitoring potential OP exposure.

Cholinesterase status, pharmacokinetics and laboratory findings during obidoxime therapy in organophosphate poisoned patients

1997 ◽  
Vol 16 (8) ◽  
pp. 473-480 ◽  
Author(s):  
H. Thiermann ◽  
U. Mast ◽  
R. Klimmek ◽  
P. Eyer ◽  
A. Hibler ◽  
...  
Keyword(s):  
Continuous Infusion ◽  
Ex Vivo ◽  
Preceding Paper ◽  
Plasma Cholinesterase ◽  
Atropine Sulphate ◽  
Impaired Liver Function ◽  
Laboratory Findings ◽  
Oxime Therapy

1 The effectiveness of oxime therapy in organophos phate poisoning is still a matter of debate. It appears, however, that the often cited ineffectiveness of oximes may be due to inappropriate dosing. By virtue of in vitro findings and theoretical considerations we concluded in the preceding paper that oximes should preferably be administered by continuous infusion following an initial bolus dose for as long as reactiva tion of inhibited acetylcholinesterase (AChE) can be expected. This conclusion has called for a clinical trial to evaluate such oxime therapy on the basis of objective parameters. 2 Before transfer to the intensive care unit (ICU), 5 patients received primary care by an emergency physician. In the ICU, atropine sulphate was adminis tered IV upon demand according to the endpoints: no bronchorrhoea, dry mucous membranes, no axillary sweating, heart rate of about 100/min. Obidoxime (Toxogonin®) was given as an IV bolus (250 mg) followed by continuous infusion of 750 mg/24 h. 3 Intoxication and therapy were monitored by determin ing erythrocyte AChE (eryAChE) activity, reactivat ability of the patient's eryAChE ex vivo, plasma cholinesterase activity, the presence of AChE inhibit ing compounds, as well as the concentrations of obidoxime and atropine in plasma. 4 Obidoxime was effective in life-threatening parathion poisoning, in particular when the dose absorbed was comparably low. In mega-dose poisoning, net reacti vation was not achieved until several days after ingestion, when the concentration of active poison in plasma had declined. Reactivatability in vivo lasted for a longer period than expected from in vitro experiments. 5 Obidoxime was quite ineffective in oxydemeton- methyl poisoning, when the time elapsed between ingestion and oxime therapy was longer than 1 day. When obidoxime was administered shortly after ingestion (1 h) reactivation was nearly complete. 6 Obidoxime levels of 10-20 μM were achieved by our regimen, and atropine could rapidly be reduced to approx. 20 nM, as attained by continuous infusion of 1 mg atropine sulphate/h. Maintenance of the desired plasma levels was not critical even when renal function deteriorated. 7 Signs of transiently impaired liver function were observed in patients who showed transient multi- organ failure. In the present stage of knowledge, we feel it advisable to keep the plasma concentration of obidoxime at 10 - 20 μM, although the full reactivating potential of obidoxime will not then be exploited. Still, the reactivation rate, with an apparent half-time of some 3 min, is twice that estimated for a tenfold higher pralidoxime concentration.

Pseudocholinesterase-mediated Hydrolysis Is Superior to Neostigmine for Reversal of Mivacurium-induced Paralysis In Vitro

1996 ◽  
Vol 84 (4) ◽  
pp. 936-938. ◽  
Author(s):  
H. S. Yang ◽  
N. Goudsouzian ◽  
J. A. J. Martyn
Keyword(s):  
Human Plasma ◽  
Positive Control ◽  
Plasma Cholinesterase ◽  
Krebs Solution ◽  
Single Twitch ◽  
Train Of Four ◽  
Human Plasma Cholinesterase ◽  
Hydrolysis Of

Background The metabolic hydrolysis of mivacurium (and succinylcholine) is markedly impaired in the presence of hereditary or acquired defects of pseudocholinesterase. Clinical reports are conflicting as to the utility of anticholinesterases, in the reversal of mivacurium paralysis. In the current study, the role of exogenous cholinesterases and/or of anticholinesterase, neostigmine, in the reversal of deep mivacurium-induced paralysis, was studied. The rat phrenic-diaphragm preparation, in a fixed volume of Krebs solution, was chosen to eliminate the confounding effects on the dissipation of neuromuscular effects caused by hydrolysis, elimination, and redistribution of the drug. Methods In the phrenic-diaphragm preparation, mivacurium was administered to obtain >90% single twitch inhibition. Single twitch responses (0.1 Hz) were monitored for 60 min, after which the response to train-of-four stimulation was tested. The reversal of mivacurium by 0.5, 1.0, or 2.0 units/ml of (true) acetylcholinesterase, bovine pseudocholinesterase, or human plasma cholinesterase and by neostigmine, 0.1, 1.0, or 10.0 micrograms/ml tested. The efficacy of human plasma cholinesterase, 1 unit/ml in combination with each of the above neostigmine concentrations, also was examined. The reversal of succinylcholine-induced paralysis by the acetylcholinesterase, bovine pseudocholinesterase, or human plasma cholinesterase (1 unit/ml) alone and in the presence of neostigmine (10.0 micrograms/ml) was additionally tested as a positive control. A train-of-four ratio > 0.75 was considered adequate reversal. Results Acetylcholinesterase was a poor hydrolyzer of mivacurium, as bioassayed by reversal of paralysis. Bovine pseudocholinesterase in concentrations of 0.5 and 1.0 units/ml did not effectively reverse single twitch and train-of-four responses by 60 min, but bovine pseudocholinesterase (2 units/ml) and all concentrations of human plasma cholinesterase did. Neostigmine alone, tested at all concentrations, was an incomplete reversal drug. Clinical or therapeutic concentrations (0.1 and 1.0 micrograms/ml) of neostigmine did not, but pharmacologic concentrations (10 micrograms/ml) interfere with the efficacy of human plasma cholinesterase (1 unit/ml). Bovine pseudocholinesterase and human plasma cholinesterase equally reversed the effects of succinylcholine but acetylcholinesterase did not, whereas the addition of 10 micrograms/ml neostigmine to the enzymes inhibited the reversal of succinylcholine. Conclusions Human plasma cholinesterase will reverse mivacurium more effectively than bovine pseudocholinesterase, but both will effectively reverse succinylcholine. Acetylcholinesterase has no effects on either relaxant. The anticholinesterase neostigmine was an incomplete reversal drug. Pharmacologic concentrations of anticholinesterases do, while clinical or therapeutic concentrations do not, completely inhibit the metabolic activity of pseudocholinesterases.

Inhibition of Human Plasma Cholinesterase in vitro by Extracts of Solanaceous Plants

Science ◽  
1958 ◽  
Vol 128 (3332) ◽  
pp. 1136-1137 ◽  
Author(s):  
W. H. ORGELL ◽  
K. A. VAIDYA ◽  
P. A. DAHM
Keyword(s):  
Human Plasma ◽  
Plasma Cholinesterase ◽  
Human Plasma Cholinesterase ◽  
Solanaceous Plants

scholarly journals INHIBITORY EFFECT OF ESMOLOL ON HUMAN PLASMA CHOLINESTERASE IN VITRO

1984 ◽  
Vol 61 (3) ◽  
pp. A308-A308 ◽  
Author(s):  
E. Barabas ◽  
T. Kirkpatrick ◽  
E. K. Zsigmond
Keyword(s):  
Human Plasma ◽  
Inhibitory Effect ◽  
Plasma Cholinesterase ◽  
Human Plasma Cholinesterase

The Role of Polyphenols in the Modulation of Plasma Non-Enzymatic Antioxidant Capacity (NEAC)

2012 ◽  
Vol 82 (3) ◽  
pp. 228-232 ◽  
Author(s):  
Mauro Serafini ◽  
Giuseppa Morabito
Keyword(s):  
Antioxidant Capacity ◽  
Dietary Intervention ◽  
Ex Vivo ◽  
The Body ◽  
Dietary Polyphenols ◽  
Enzymatic Antioxidant ◽  
Endogenous Antioxidant

Dietary polyphenols have been shown to scavenge free radicals, modulating cellular redox transcription factors in different in vitro and ex vivo models. Dietary intervention studies have shown that consumption of plant foods modulates plasma Non-Enzymatic Antioxidant Capacity (NEAC), a biomarker of the endogenous antioxidant network, in human subjects. However, the identification of the molecules responsible for this effect are yet to be obtained and evidences of an antioxidant in vivo action of polyphenols are conflicting. There is a clear discrepancy between polyphenols (PP) concentration in body fluids and the extent of increase of plasma NEAC. The low degree of absorption and the extensive metabolism of PP within the body have raised questions about their contribution to the endogenous antioxidant network. This work will discuss the role of polyphenols from galenic preparation, food extracts, and selected dietary sources as modulators of plasma NEAC in humans.

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