Plasma Pseudocholinesterase Research Articles

Determination of succinylcholine in tissues by TLC, GC/NPD, and GC/MS.

Succinylcholine, a bis-quaternary ammonium compound, is considered an elusive analyte due to rapid hydrolysis by pseudocholinesterase in plasma. However, tissue acetylcholinesterase is relatively inactive toward this substrate. Hence, analysis of tissues of succinylcholine-treated animals may reveal the presence of unchanged drug. This report describes three chromatographic techniques (TLC, GC/NPD, and GC/MS) which may be applied to the analysis of this substance in human tissues. Validation of the techniques was accomplished using tissues from rats treated with succinylcholine.

Plasma pseudocholinesterase: A potential marker for early detection of obesity

Plasma pseudocholinesterase activity, body weight and food intake showed significantly higher values in obese (ob/ob) mice than their lean littermates starting at the age of 35 days. The enzyme activity also showed a good positive correlation with age, body weight and food intake in all the mice from this age. Analysis of the data also indicated that between 35 and 58 days of age, pseudocholinesterase activity appeared to be more sensitive than body weight measurements in predicting obesity. Diabetic (db/db) mice on restricted diet, showed no significant difference in plasma pseudocholinesterase activity between the pre and post restricted blood samples. In contrast, diabetic mice on a non-restricted diet showed a significant increase in enzyme activity during the same interval of time. This suggests a relationship between hyperphagia, pseudocholinesterase and obesity.

Subacute toxicity in rats of orally administered fenitrothion alone and in a selected formulation

Young adult male and female Sprague-Dawley rats received 1.0, 5.0, 10.0, or 20.0 mg/kg body wt of technical fenitrothion ( O,O-dimethyl O-(4-nitro- m-tolyl)phosphorothioate) in ethanol:propylene glycol (25:75) in the absence or presence of 1.5% ( v v ) of each of Atlox 3409F (emulsifier) and Dowanol TPM (cosolvent) by daily gavage for 30 consecutive days. At 7, 14, 21, and 30 days of treatment, five randomly selected rats from each treatment group were killed; tissues (liver, kidney, brain, spinal cord, and distal sciatic nerve) were preserved for morphological examination. The effects of treatment were assessed by measuring changes in blood plasma pseudocholinesterase (ψChE), erythrocytic and brain acetylcholinesterase (AChE), and hepatic and renal nonspecific carboxylesterase (CE) as well as routine hematology and serum biochemistry. At 8, 30, 60, and 90 days after treatment, five animals of each group were killed to assess the reversibility of any observed biochemical, physiological, or histopathological effects. No changes in the routine hematological and serum biochemical parameters or in tissue morphology were observed which could be related either to the vehicle, emulsifier(s)-cosolvent, or to a dose-dependent effect of fenitrothion. A dose-dependent inhibition of the tissue esterases was observed at doses above 1.0 mg fenitrothion/kg body wt. Recovery of esteratic activity from the treatment was rapid except for those rats receiving the largest dose; however, within 2 months after treatment, the activities of all treated rats were comparable to control activities. The emulsifier (Atlox 3409F) and the cosolvent (Dowanol TPM), at concentrations routinely employed in aerial spraying formulations, did not substantially enhance or reduce the toxicity of fenitrothion.

Cholinesterase enzymes in the blood of patients with Alzheimer's disease

Plasma pseudocholinesterase activity was about 100% higher in patients with Alzheimer's-type dementia than in similar age controls. Red cell acetylcholinesterase activity tended to be lower in patients than controls. Administration of lecithin substantially increased plasma choline levels but did not alter activity of either of the cholinesterase enzymes.

Effect of adrenaline, acetylcholine and histamine on pseudocholinesterase (EC 3.1.1.8) activity in blood plasma of quails

Intramuscular injection of adrenaline and acetylcholine (2 μg/100 g body wt) after 1 min significantly increased the activity of pseudocholinesterase in plasma of quails. Histamine (2 μg/100 g body wt) did not influence this enzyme activity.

Species variation in plasma cholinesterase activity

1. Plasma from 26 animal species has been examined for pseudocholinesterase activity, measured against butyrylcholine, and the electrophoretic mobility of an acylhydrolase. 2. There is similarity in activity between the species in each Order but considerable differences between some Orders. 3. Plasma pseudocholinesterase activity is unlikely to provide other than a very approximate guide to the susceptibility of species to paralysis by succinylcholine.

Chronic toxicity of technical fenitrothion in male rats

Weanling male Wistar rats were given 0.5, 1.0, 5.0 or 10.0 mg/kg body wt of technical fenitrothion ( O,O-dimethyl O-(4-nitro- m-tolyl) phosphorothioate in peanut oil by daily oral gavage for 12 months. Each month, 10 vehicle-and 5 insecticide-treated rats from each group were killed, tissues (liver, kidney, brain, spinal cord, and sciatic nerve) were preserved for morphological examination and the effects of treatment were assessed by measuring changes in activities of blood plasma pseudocholinesterase, erythrocytic and brain acetylcholinesterase (AChE), and hepatic and renal nonspecific carboxylesterases (CE) as well as routine hematology and serum biochemistry. At 12 months, administration was stopped and the survivors were held for an additional 2 months to monitor the recovery from the biological effects of the treatment. No changes were observed in the routine hematological or serum biochemical parameters measured during the treatment period at any of the doses administered. The morphological changes observed could not be related either to the vehicle or to a dose-dependent effect of fenitrothion. A dose-dependent inhibition of the tissue esterases was observed. Little change was measured at 0.5 and 1.0 mg/kg/day. Marked reductions in hepatic CE, brain, and erythrocytic AChE activities were observed at doses of 5.0 and 10.0 mg/kg/day within 1 month of treatment and remained relatively constant for the duration of treatment. Within 1 month after treatment was stopped, tissue esterase levels were within normal limits with the exception of the brain AChE in rats given the two larger doses. Within 2 months after treatment was terminated, tissue esterase activities of all treated rats were comparable to control activities.

The acute toxicity of fenitrothion in weanling rats and effects on tissue esterases and mono-oxygenases

Summary Weanling male Wistar rats received 50 mg fenitrothion/kg body wt/day dissolved in peanut oil by oral gavage for 5 consecutive days. Overt signs of toxicity were observed within 30 min of receiving the third dose. Severely affected animals were killed for the analysis of tissue esterase activities and insecticide residues and to assess the influence of this insecticide on hepatic microsomal mono-oxygenase activities. Daily treatment was terminated after 5 such doses and the survivors were killed at suitable intervals afterward to assess the recovery of tissue esterases. Fenitrothion caused a significant reduction in liver and body weights, marked changes in pentobarbitone sleeping time and in hepatic microsomal mono-oxygenase ( p -nitroanisole O -demethylase, aniline hydroxylase) activities. Marked inhibition of plasma pseudocholinesterase (PChE), hepatic and renal non-specific carboxylesterases (CE) and erythrocytic and brain acetylcholinesterase (AChE) occurred. Recovery from 5 such daily doses was slow for all tissue esterases with the exception of PChE which returned to 78% of control activity values within 5 days. Activities of the other tissue esterases were 20–50% of normal at 5 days and only 70–90% of normal at 16 days after the final dose.

Etomidate and plasma esterase activity in man and experimental animals.

No hydrolysis of etomidate in plasma in vitro was detected in samples from man, horse, cow, sheep, guinea pig or white rabbit. Brown rabbits showed a moderate degree of hydrolysis and it was marked in plasma from Wistar rats. In this species, a single enzyme, an alliesterase, participated in the hydrolysis in plasma. Etomidate did not interfere with the hydrolysis of procaine by plasma pseudocholinesterase in man.

Clinical Pharmacokinetics of Local Anaesthetics1

The introduction of the new long acting local anaesthetics, bupivacaine and etidocaine, has stimulated an expansion of interest in regional anaesthesia, particularly for obstetrical applications and pain therapy. System toxicity following injection of local anesthetics occurs albeit infrequently, and tentative correlations have been made between the onset of CNS and cardiovascular effects and circulating drug concentrations in both adults and neonates. Amongst other factors, interpretation of these relationships depends upon blood distribution and plasma binding of the agents, sampling sites and acid-base balance. The disposition kinetics and placental transfer of the amide type agents have been well characterised. In adults their clearance is almost entirely hepatic but in neonates an increase in the renal component is, in part, a reflection of the immaturity of some of the enzymes responsible for their metabolism. Ester type agents are rapidly hydrolysed by plasma pseudocholinesterase and this has led to a preference for chloroprocaine in some obstetric procedures. Major determinants of the systemic absorption of the agents after perineural administration include their physicochemical and vasoactive properties, perfusion and tissue binding at the site of injection and whether or not adrenaline has been added. In respect of blood drug concentrations achieved after various regional anaesthetic procedures, the margin of systemic safety appears to favour bupivacaine and etidocaine compared to shorter acting analogues such as lignocaine and mepivacaine. The time course of local anaesthetic remaining at the site of injection has been calculated following intravenous regional anaesthesia and peridural block. This has allowed prediction of the local and systemic accumulation of the drugs following contined dosage. Blood concentrations of local anaesthetics after perineural injection are not closely related to age, weight or pregnancy but may be influenced by diseases associated with haemodynamic changes and by other drugs given at or around the time of regional blockade.

Plasma Pseudocholinesterase Deficiency Associated with Diethylstilbestrol Therapy

Plasma Pseudocholinesterase Deficiency Associated with Diethylstilbestrol Therapy

Effect of glucocorticoids on liver and blood cholinesterases

The effects of oral prednisone on plasma and red blood cell cholinesterases have been studied in human volunteers. While the activity of plasma pseudocholinesterase is depressed by glucocorticoid administration, the activity of red blood cell true cholinesterase is not affected. Cortisol administration to rats, intraperitoneal or subcutaneous, inhibited liver pseudocholinesterase activity, indicating a possible depression of the enzyme protein synthesis.

Pharmacokinetics of intravenous anaesthetics: implications for clinical use.

Intravenous anaesthetics comprise a variety of drugs that differ in chemical structure but share a suitable combination of physical properties that confer ready penetration of the blood-brain barrier. Lipid solubility is particularly important in this respect. Rapid entry into the brain is associated with rapid distribution and redistribution in the body for most of these drugs. They all readily cross the placenta to the fetus. Rate of metabolism varies between the rapidly biotransformed drugs like propanidid to the slowly metabolised ones like thiopentone. The liver is the main site of biotransformation, with the exception of propanidid which is hydrolysed by plasma pseudocholinesterase. Recovery of mental and psychomotor functions is protracted compared with inhalation anaesthetics, except after propanidid.

Plasma Factor XIII and Platelet Factor XIII in Hyperlipaemia

Plasma factor XIII activity measured by a quantitative assay was found to be significantly higher in hypertriglyceridaemic patients (type IV and combined hyperlipoproteinaemia), as compared to normolipaemic controls. No such elevation in plasma factor XIII activity was found in patients with type Ha hyperlipaemia. Plasma pseudocholinesterase was found to parallel the elevated factor XIII activity in hypertriglyceridaemic subjects. In contrast, platelet factor XIII activity was not raised in hyperlipaemic subjects, and plasma factor XIII was found to be normal in a normolipaemic subjects with thrombocythaemia. It was concluded that there is no significant contribution from platelets to plasma factor XIII activity, and that the observed increase in plasma factor XIII in hypertriglyceridaemia results from enhanced hepatic synthesis of the enzyme.

Parathion administration in the monkey: Time course of inhibition and recovery of blood cholinesterases and visual discrimination performance

The effects of parathion [ O,O-diethyl O- p-nitrophenyl phosphorothionate] administration on activities of acetyl-cholinesterase (AChE) in blood and pseudocholinesterase (ChE) in plasma were studied in bonnet ( Macaca radiata) and rhesus ( M. mulatta) monkeys. In addition, the effects of parathion administration on performance of learned visual discrimination tasks were studied in rhesus monkeys. Peak inhibition of AChE and ChE occurred about 6 hr after administration of 0.5, 1.0, and 2.0 mg/kg parathion po. The degree of peak inhibition was greater for ChE than for AChE, was dose-related for both enzymes, and was of about the same magnitude in both species, even though control values for AChE and ChE differed in the two species. Activities of both enzymes returned to control values within 2 wk at all dose levels. Administration of 2.0, 1.5, and 1.0 mg/kg parathion abolished performance of the learned tasks 5 hr later and for as long as 3–7 days. When performance of the tasks returned after the 2.0 mg/kg dose, the level of performance remained below pretreatment values for up to 3 wk. A dose of 0.5 mg/kg did not affect performance. Comparison of the present findings with other work showed that reversal of blood AChE and ChE inhibition after parathion administration occurred more rapidly in monkey than in man but required more time in monkey than in mouse. It was observed that scopolamine and methyl scopolamine also blocked visual discrimination performance.

Succinylcholine and Pseudocholinesterase

To the Editor.— With the intensified use of organophosphorous insecticides by the general population and the increasing use of succinylcholine in general as well as in dental surgery, we would like to point out a problem that has come to our attention. Humans as well as other species have a specific acetylcholinesterase that is present at the cholinergic junctions of the nervous system and can be measured in red blood cells. In addition, pseudocholinesterase, a plasma enzyme, has no known physiological role but is essential for the rapid degradation of succinylcholine, a muscle relaxant. Levels of this enzyme can be depressed as a result of hepatocellular disease, or exposure to anticholinesterase agents such as the organophosphorous pesticides (Parathion, DDVP, Methylparathion, Demeton). A low plasma pseudocholinesterase level will increase sensitivity to succinylcholine, cause prolonged postoperative apnea, and may result in death from respiratory failure. Pseudocholinesterase catabolizes several drugs used in anesthesia

Perinatal development of human blood esterases.

Erythrocyte acetylcholinesterase, plasma proteins, pseudocholinesterase, and arylesterase development was investigated in groups of premature infants of varying gestational ages, comparing the detected levels with those observed in groups of healthy older children and adults. A rapid increase in protein concentration was evident between 28 and 40 weeks gestation, followed by a slower rate of increase until 1 year of age. A rapid increase in plasma pseudocholinesterase and arylesterase activity occurred from 28 weeks gestation to 1 year of age, with no significant changes in activities from those of adults occurring after 1 year. In contrast, the erythrocyte acetylcholinesterase levels increased most markedly between 40 weeks gestation and 1 year of age. Premature infant plasma degraded procaine hydrochloride and insecticide paraoxon more slowly than full‐term infants, while the rates of hydrolysis for these 2 groups were significantly lower than those detected for children older than 1 year or for adults.

A specific radioisotopic assay for acetylcholinesterase and pseudocholinesterase in brain and plasma

A radiometric procedure for assaying acetyl and pseudocholinesterase is presented. The method is based on the adsorption of unreacted substrates as their acid-1- 14C choline esters on Amberlite CG-120 resin suspended in dioxane. The supernatant solution containing the product of hydrolysis, the free acid-1- 14C, is counted in a liquid scintillation spectrometer. Blank values are less than 0.5% of the total radioactivity added initially and assays may be made with 0.01–1 mg of rat brain tissue or 0.01–1 μl of rat plasma. The method can be used for short or long term incubations. Rates of hydrolysis are presented for three substrates, Mecholyl, acetylcholine, butyrylcholine, with mouse, rat, guinea pig, rabbit, and bovine brain. Plasma values are given for rat and human plasma. Two specific inhibitors, BW 284C51 and iso-OMPA were shown to support the relative specificity of the procedure for acetylcholinesterase and pseudocholinesterase when specific substrates are employed.

Rapid screening test for serum cholinesterase.

Abstract A simple and reliable screening test, helpful in detecting low plasma pseudocholinesterase level and pseudocholinesterase variants, is described. The test depends upon the different reactions of variants of the enzyme in the hydrolysis of butyrylthiocholine. The results of the screening test using sera with different variants is presented, and this result is compared with already established criteria used to assess phenotypes.

Hereditary deficiency of pseudocholinesterase in Eskimos.

HIGH susceptibility to the neuromuscular blocking action of succinylcholine is usually associated with a defective form of pseudocholinesterase in blood plasma; the abnormal enzyme is distinguished by its resistance to inhibition by dibucaine1. The gene frequency of this abnormality in Caucasians is estimated to be 0.019; 3.8 per cent of the population are heterozygous; and 1 in 2,800 individuals is sensitive to succinylcholine2.