For quantitative determination of acetylcholinesterase activity and evaluation of acetylcholinesterase inhibitors.

Method: OD412nm.
Samples: blood, serum, plasma etc.
Species: all.
Procedure: 10 min.
Size: 100 tests.
Detection limit: 10 U/L.

DESCRIPTION

ACETYLCHOLINESTERASE (EC 3.1.1.7, AChE), also known as RBC
cholinesterase, is found primarily in the blood and neural synapses.
Low serum cholinesterase activity may relate to exposure to
insecticides or to one of a number of variant genotypes. AChE
catalyzes the hydrolysis of the neurotransmitter acetylcholine into
choline and acetic acid, a reaction necessary to allow a cholinergic
neuron to return to its resting state after activation. Cholinesterase
levels of cells and plasma are used as a guide in establishing safety
precautions relative to exposure and contact, as well as a guide in
determining the need for workers to be removed from areas of contact
with the organic phosphate insecticides.
Simple, direct and automation-ready procedures for measuring AChE
activity are very desirable. BioAssay Systems' QuantiChromTM
Acetylcholinesterase Assay is based on an improved Ellman method,
in which thiocholine produced by the action of acetylcholinesterase
forms a yellow color with 5,5’-dithiobis(2-nitrobenzoic acid). The
intensity of the product color, measured at 412 nm, is proportionate to
the enzyme activity in the sample.

APPLICATIONS

Direct assays of acetylcholinesterase activity in blood, serum, plasma,
and other biological samples. Evaluation of acetylcholinesterase
inhibitors.

KEY FEATURES

Sensitive and accurate. Detection range 10 to 600 U/L AChE activity
in 96-well plate assay.
Convenient. The procedure involves adding a single working reagent,
and reading the optical density at 2 min and 10 min at room
temperature.
High-throughput. Can be readily automated as a high-throughput 96-
well plate assay for thousands of samples per day.

KIT CONTENTS

(100 tests in 96-well plates)
Assay Buffer (pH 7.5): 30 mL Reagent: 240 mg
Calibrator: 4 mL (equivalent to 200 U/L)

Storage conditions. The kit is shipped at room temperature. Store all
reagents at room temperature. Shelf life: 6 months after receipt.
Precautions: reagents are for research use only. Normal precautions
for laboratory reagents should be exercised while using the reagents.

MATERIALS REQUIRED, BUT NOT PROVIDED

Pipeting (multi-channel) devices. Clear-bottom 96-well plates (e.g.
Corning Costar) and plate reader.

Sample Type: cerebral cortical tissues

Species:  rat

References: Basselin, M et al (2009). Acute but not chronic donepezil increases muscarinic receptor-mediated signaling via arachidonic acid in unanesthetized rats. J Alzheimers Dis. 17(2):369-82

Pubmed ID: 19363262

Pubmed link: http://www.ncbi.nlm.nih.gov/pubmed?term=19363262

Abstract:

Donepezil, an acetylcholinesterase (AChE) inhibitor used for treating Alzheimer's disease patients, is thought to act by increasing brain extracellular acetylcholine (ACh), and ACh binding to cholinergic receptors. Muscarinic receptors are coupled to cytosolic phospholipase A2 (cPLA2) activation and arachidonic acid (AA) release from synaptic membrane phospholipid. This activation can be imaged in rodents as an AA incorporation coefficient k*, using quantitative autoradiography. Acute and chronic effects of donepezil on the AA signal, k* for AA, were measured in 81 brain regions of unanesthetized rats. Twenty min after a single oral dose (3.0 mg/kg) of donepezil, k* was increased significantly in 37 brain regions, whereas k* did not differ from control 7 h afterwards or following chronic (21 days) of donepezil. Pretreatment with atropine prevented the 20-min increments in k* following donepezil. Donepezil also increased the brain ACh concentration and reduced brain AChE activity, but did not change cPLA2 activity, regardless of administration regimen. These results show that donepezil acutely increases the brain AA signal that is mediated by ACh acting at muscarinic receptors, but that this signal is rapidly desensitized despite continued elevated brain ACh concentration. In contrast, the AA signal in response to arecoline was not altered following donepezil.

 [PubMed - indexed for MEDLINE] PMCID: PMC2790024

Sample Type: serum

Species:  human

References: Al-Akwa, AA et al (2009). Free radicals are present in human serum of Catha edulis Forsk (Khat) abusers. J Ethnopharmacol. 125(3):471-3

Pubmed ID: 19619634

Pubmed link: http://www.ncbi.nlm.nih.gov/pubmed?term=19619634

Abstract:

OBJECTIVE: Khat (Catha edulis Forsk) is a naturally occurring drug with an amphetamine-like structure and action. It has been postulated that amphetamine induces free radical formation. On this basis, we have hypothesized that Khat may promote synthesis of reactive oxygen and nitrogen species in the same way that amphetamine promotes free radical production.

MATERIALS AND METHODS: Forty male subjects were enrolled in two groups: those with a chronic Khat chewing habit (n=20), and those without a chewing habit (controls; n=20). Both groups were matched with regard to age. Total antioxidant capacity and cholinesterase (AChE) activity were assayed.

RESULTS: This study showed that Khat consumption inhibited serum free radical scavenging enzymes, resulting in significant elevations in free radical loads (p=0.01; n=20). We also showed that serum acetyl cholinesterase (AChE) was significantly inhibited in the Khat chewing group (p=0.002; n=20).

CONCLUSION: These results show for the first time that Khat may contribute to high levels of free radicals. In addition, the presence of pesticides in Khat leaves is implicated in the inhibition of AChE activity.

 [PubMed - indexed for MEDLINE]

Sample Type: explanted atria

Species:  dog

References: Ng, J et al (2011). Autonomic remodeling in the left atrium and pulmonary veins in heart failure: creation of a dynamic substrate for atrial fibrillation. Circ Arrhythm Electrophysiol.4(3):388-96

Pubmed ID: 21421805

Pubmed link: http://www.ncbi.nlm.nih.gov/pubmed?term=21421805

Abstract:

BACKGROUND: Atrial fibrillation (AF) is commonly associated with congestive heart failure (CHF). The autonomic nervous system is involved in the pathogenesis of both AF and CHF. We examined the role of autonomic remodeling in contributing to AF substrate in CHF.

METHODS AND RESULTS: Electrophysiological mapping was performed in the pulmonary veins and left atrium in 38 rapid ventricular-paced dogs (CHF group) and 39 control dogs under the following conditions: vagal stimulation, isoproterenol infusion, ?-adrenergic blockade, acetylcholinesterase (AChE) inhibition (physostigmine), parasympathetic blockade, and double autonomic blockade. Explanted atria were examined for nerve density/distribution, muscarinic receptor and ?-adrenergic receptor densities, and AChE activity. In CHF dogs, there was an increase in nerve bundle size, parasympathetic fibers/bundle, and density of sympathetic fibrils and cardiac ganglia, all preferentially in the posterior left atrium/pulmonary veins. Sympathetic hyperinnervation was accompanied by increases in (1)-adrenergic receptor R density and in sympathetic effect on effective refractory periods and activation direction. ?-Adrenergic blockade slowed AF dominant frequency. Parasympathetic remodeling was more complex, resulting in increased AChE activity, unchanged muscarinic receptor density, unchanged parasympathetic effect on activation direction and decreased effect of vagal stimulation on effective refractory period (restored by AChE inhibition). Parasympathetic blockade markedly decreased AF duration.

CONCLUSIONS: In this heart failure model, autonomic and electrophysiological remodeling occurs, involving the posterior left atrium and pulmonary veins. Despite synaptic compensation, parasympathetic hyperinnervation contributes significantly to AF maintenance. Parasympathetic and/or sympathetic signaling may be possible therapeutic targets for AF in CHF.

 [PubMed - indexed for MEDLINE]

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