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.

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.

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
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