Cholinesterases serum

Roan CC, Morgan DP, Cook N, et al. 1969. Blood cholinesterases, serum parathion concentrations and urine p-nitrophenol concentrations in exposed individuals. Bull Environ Contam Toxicol 4 362-369. 

In this drug class, only sucdnylcholine (succinyldicholine, suxamethonium, AJ is of clinical importance. Structurally, it can be described as a double ACh molecule. Like ACh, succinylcholine acts as agonist at endplate nicotinic cholino-ceptors, yet it produces muscle relaxation. Unlike ACh, it is not hydrolyzed by acetylcholinesterase. However, it is a substrate of nonspecific plasma cholinesterase (serum cholinesterase, p. 100). 

Blood Cholinesterase, Serum Para-thion Concentrations, and Urine p-Nitrophenol Concentrations in Exposed Individuals Bull. Environ. Contam. Toxicol. 4(6) 362-369 (1969) CA 72 77892m... 

A Crystalline Serum Mucoprotein with High Cholinesterase Activity, R. Bader, F. Schultz, and M. Stacey,Nature, 154(1944) 183-184. 

Methyl paraoxon may also be made unavailable by binding to noncritical tissue and plasma constituents (Benke and Murphy 1975), including cholinesterase (Parkinson 1996). In addition, the parent compound is bound to albumin, in serum, as discussed previously in Section 3.4.2.4, but this binding does not appear to limit the availability of methyl parathion to the tissues, indicating that it is reversible. Tissue binding appears to be more important than serum binding (Braeckman et al. 1980, 1983). 

There is a second type of cholinesterase called butyrylcholinesterase, pseudocholinesterase, or cholinesterase. This enzyme is present in some nonneural cells in the central and peripheral nervous systems as well as in plasma and serum, the liver, and other organs. Its physiologic function is not known, but is hypothesized to be the hydrolysis of esters ingested from plants (Lefkowitz et al. 1996). Plasma cholinesterases are also inhibited by organophosphate compounds through irreversible binding this binding can act as a detoxification mechanism as it affords some protection to acetylcholinesterase in the nervous system (Parkinson 1996 Taylor 1996). 

Diagnosis of organophosphate poisoning (including methyl parathion) can be confirmed by evaluation of serum (plasma) cholinesterase and erythrocyte cholinesterase. However, cholinesterase inhibition is not specific for organophosphates. For example, carbamate insecticides also result in cholinesterase inhibition, which is usually transitory. Erythrocyte cholinesterase measurement is a specific test for... 

A classification of organophosphate poisoning has been proposed by Tafuri and Roberts (1987) modified from Namba et al. (1971). Clinical signs and symptoms of intoxication may occur when serum cholinesterase levels drop to below 50% of the normal value. Mild poisoning, with the patient still ambulatory, may occur when serum cholinesterase levels are 20-50% of normal moderate poisoning with inability to walk with levels 10-20% of normal and severe poisoning with respiratory distress and unconsciousness with serum cholinesterase levels <10% of normal. 

Many pesticides are neurotoxicants poisoning the nervous system. A number of pesticides are acetyl cholinesterase inhibitors (Serat and Mengle 1973). Generally, pesticides determination has been performed by GC since the 1960 s (Morrison and Durham 1971 Fournier et al. 1978). There are no reference materials for pesticides in urine or serum, although as with PAHs there are a number biological matrices certified for the content of various pesticides available for environmental food and agriculture analysis and which may have some application in clinical chemistry. 

FMC. 1991a. The effects of Durad 125 on serum cholinesterase and brain neuropathy. Target esterase activity in male Long-Evans rats. Study No 64460. FMC Corporation, Princeton, NJ. 

Lockridge, O., Bartels, C.F., Vaughan, T.A., Wong, C.K., Norton, S.E. and Johnson, L.L. (1987) Complete amino acid sequence of human serum cholinesterase. Journal of Biological Chemistry 262, 549-557. 

All groups seemed normal at day 150 no difference in blood or serum cholinesterase activity... 

Petruccioli, L. and P. Turillazzi. 1991. Effect of methylmercury on acetylcholinesterase and serum cholinesterase activity in monkeys, Macaca fascicularis. Bull. Environ. Contam. Toxicol. 46 769-773. 

C. carpio 5 initial reduction by 50% of serum cholinesterase activity which gradually increased to 130% of control values during exposure for 2 weeks, suggesting that paraquat may influence resynthesis of acetylcholinesterase 28... 

Chetty KN, Walker J, Brown K, et al. 1993a. The effects of dietary calcium and chlordecone on cholinesterase, triglycerides, low density lipoproteins, and cholesterol in serum of rat. Arch Environ Contam Toxicol 24 365-367. 

There is some confusion in the literature regarding the substances designated as anti-choline-esterases (usually shortened to anticholinesterases). The term cholinesterase was first used1 in connexion with an enzyme present in the blood serum of the horse which catalysed the hydrolysis of acetylcholine and of butyrylcholine, but exhibited little activity towards methyl butyrate,... 

Thus a distinction was provided between simple esterases, such as fiver esterase, which catalysed the hydrolysis of simple aliphatic esters but were ineffective towards choline esters. The term 1 cholinesterase was extended to other enzymes, present in blood sera and erythrocytes of other animals, including man, and in nervous tissue, which catalysed the hydrolysis of acetylcholine. It was assumed that only one enzyme was involved until Alles and Hawes2 found that the enzyme present in human erythrocytes readily catalysed the hydrolysis of acetylcholine, but was inactive towards butyrylcholine. Human-serum enzyme, on the other hand, hydrolyses butyrylcholine more rapidly than acetylcholine. The erythrocyte enzyme is sometimes called true cholinesterase, whereas the serum enzyme is sometimes called pseudo-cholinesterase. Stedman,3 however, prefers the names a-cholinesterase for the enzyme more active towards acetylcholine, and / -cholinesterase for the one preferentially hydrolysing butyrylcholine. Enzymes of the first type play a fundamental part in acetylcholine metabolism in vivo. The function of the second type in vivo is obscure. Not everyone agrees with the designation suggested by Stedman. It must also be stressed that enzymes of one type from different species are not always identical in every respect.4 Furthermore,... 

Their specimen of cholinesterase was prepared from horse serum by the method of Stedman and Stedman,1 and the method of estimation was that of Ammon.2 The enzyme solution was placed in the right-hand flask of a Barcrofb manometer, in a total volume of 3 ml. of 0-2 per cent NaHC03 solution the gas phase was 5 per cent C02 in Na. The reaction, carried out at 20°, was started by adding a solution containing 2 mg. of acetylcholine chloride. The C02 output was usually linear until about 100 fi. had been produced. 

Fig. 12. Progress curve of inhibition of horse-serum cholinesterase by eserine and by di -isopropyl phosphorofluoridate in the absence of a substrate at pH 7-4 and 20°. x---x, 5x 10 8 M eserine O—O.ca. 3 x 10-10 M di-isopropyl phosphorofluoridate.

Effect of substrate concentration. In the following experiments the cholinesterase activities were measured by a continuous titration method. The digest of acetylcholine and horse-serum cholinesterase (total vol. 10 ml.), containing bromothymol blue and 0-0002 m phosphate, was titrated with 0-01 n NaOH to maintain the pH at 7-4. The titrations, which were carried out at 20°, were linear over a period of 10-15 min. The velocity was expressed as ml. 0-01 n NaOH/5 min. under the conditions used, it was proportional to the enzyme concentration. When an inhibitor was added, this was equilibrated with the enzyme, etc., for 5 min. at 20° before adding the substrate contained in a volume of 1 ml. 

Fig. 13. Effect of substrate concentration on inhibition of horse-serum cholinesterase.1 Enzyme activity was estimated by titration with 0-01 n NaOH at pH 7-4 and 20°. — , control, no inhibitor x — x, 2x 10 7 m eserine 0—O, 5 x 10 8 m di-isopropyl phosphorofluoridate.

True and pseudo-cholinesterase. The above serum preparations contained both the true and pseudo- cholinesterases of Mendel and Rudney.1 The effect of di-isopropyl phosphorofluoridate on these components was examined separately by means of the specific substrates described by Mendel, Mundel and Rudney,2 using the titration method described above. Phosphorofluoridate (5 x 10 8m) gave an inhibition of 57 per cent of the activity towards 00045m acetylcholine, 30 per cent of the activity towards 0-0005 m acetyl-/ methyl-choline, and 40 per cent of that towards 0-005 m benzoylcholine, after incubating the enzyme with the poison for 5 min. Thus in these experiments there appeared to be no appreciable difference in sensitivity of the true and pseudo-cholinesterases of horse serum to phosphorofluoridates. 

Fig. 14. Inhibition of horse-serum cholinesterase by various compounds. Incubated for 15 min. at 20° before addition of 2 mg. of acetylcholine chloride. A, di-isopropyl phosphorofluoridate B, di ec.-butyl phosphorofluoridate C, eserine D, diphenyl phosphorofluoridate E, dithioethyl phosphorofluoridate F, tetramethylphosphorodiamidic fluoride O, diethyl ALmethylphosphor-amidate.

Inhibitory power of eserine, phosphorofluoridates and related compounds on horse-serum cholinesterase... 

The rate of regeneration of plasma cholinesterase in man after its depression by D.F.P. was found to resemble the rate of regeneration of serum albumin in experimental animals that have been depleted by plasmaphoresis.1... 

The rate of regeneration of serum cholinesterase in normal subjects after the administration of D.F.P. by intramuscular injection has been determined.1 The regeneration rate of serum cholinesterase after the administration of D.F.P. to patients with liver damage has also been determined and is found to be significantly lower than normal. 

It will be shown below that D.F.P. is rapidly destroyed in vitro and in vivo.2 Therefore, the recovery of serum cholinesterase activity is not representative of a reversal of enzyme inhibition, but is indicative of synthesis of new enzyme proteins. Since the regeneration rate of serum cholinesterase in patients with liver damage is significantly depressed as contrasted with that in the normal patient, it is concluded that the ability of such patients to synthesize this particular enzyme protein is decreased. This constitutes evidence for the view that the fiver is a primary locus for the formation of serum cholinesterase. 

The enzymes used by these workers were cholinesterase, prepared from horse serum, and horse-liver esterase. Parallel experiments were carried out with twice crystallized ovalbumin, and with an aged, dialysed specimen of horse serum with negligible esterase activity. 

As stated previously (pp. 62 etseq.) there is often correlation between anticholinesterase activity in vitro and gross mammalian toxicity. The toxicity of O.M.P.A. is not very muoh less than that of tabun, D.F.P. and T.E.P.P., yet the anti-cholinesterase activity of O.M.P.A. in vitro is negligible (50 per cent inhibition, 4-5x10 2m). On the other hand, O.M.P.A. produces all the symptoms of acetylcholine poisoning when administered to animals. Moreover, the serum cholinesterase of such animals is almost completely inhibited. Another anomaly of O.M.P.A. is that toxic action is slower than that of D.F.P. or tabun, an hour s delay being usual compared to the very quick knock-out action of D.F.P., etc. (see p. 2). 

It was found that catechol derivatives in general were able to protect cholinesterases in vitro. Both horse-serum and rat-brain cholinesterases were protected against the above inhibitors. It is thought that the basis of the protection is a reaction between catechol and the inhibitor. 

Inhibition of the two principal human cholinesterases, acetylcholinesterase and pseudocholinesterase, may not always result in visible neurological effects (Sundlof et al. 1984). Acetylcholinesterase, also referred to as true cholinesterase, red blood cell cholinesterase, or erythrocyte cholinesterase is found in erythrocytes, lymphocytes, and at nerve synapses (Goldfrank et al. 1990). Inhibition of erythrocyte or lymphocyte acetylcholinesterase is theoretically a reflection of the degree of synaptic cholinesterase inhibition in nervous tissue, and therefore a more accurate indicator than pseudocholinesterase activity of inhibited nervous tissue acetylcholinesterase (Fitzgerald and Costa 1993 Sundlof et al. 1984). Pseudocholinesterase (also referred to as cholinesterase, butyrylcholinesterase, serum cholinesterase, or plasma cholinesterase) is found in the plasma, serum, pancreas, brain, and liver and is an indicator of exposure to a cholinesterase inhibitor. 

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