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Slavica Vučinić, Milica Zlatković, Biljana Antonijević, Marijana Ćurčić and Bogdan Bošković

Despite improvements to intensive care management and specific pharmacological treatments (atropine, oxime, diazepam), the mortality associated with organophosphate (OP) poisoning has not substantially decreased. The objective of this examination was to describe the role of fresh frozen plasma (FFP) in acute OP poisoning. After a deliberate ingestion of malathion, a 55-year-old male suffering from miosis, somnolence, bradycardia, muscular fasciculations, rales on auscultation, respiratory insufficiency, as well as from an inhibition of red blood cell acetylcholinesterase (AChE) and plasma butyrylcholinesterase (BuChE), was admitted to hospital. Malathion was confirmed in a concentration of 18.01 mg L-1. Apart from supportive measures (including mechanical ventilation for four days), antidotal treatment with atropine, oxime - pralidoxime methylsulphate (ContrathionR), and diazepam was administered, along with FFP. The potentially beneficial effects of FFP therapy included a prompt increase of BuChE activity (from 926 IU L-1 to 3277 IU L-1; reference range from 7000 IU L-1 to 19000 IU L-1) and a reduction in the malathion concentration, followed by clinical recovery. Due to BuChE replacement, albumin content, and volume restitution, FFP treatment may be used as an alternative approach in patients with acute OP poisoning, especially when oximes are not available.

Open access

Zrinka Kovarik, Ana Vrdoljak, Suzana Berend, Maja Katalinić, Kamil Kuča, Kamil Musilek and Božica Radić

Evaluation of Oxime K203 as Antidote in Tabun Poisoning

We studied bispyridinium oxime K203 [(E)-1-(4-carbamoylpyridinium)-4-(4-hydroxyiminomethylpyridinium)-but-2-ene dibromide] with tabun-inhibited human acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in vitro, and its antidotal effect on tabun-poisoned mice and rats in vivo. We compared it with oximes K048 and TMB-4, which have proven the most efficient oxime antidotes in tabun poisoning by now. Tabun-inhibited AChE was completely reactivated by K203, with the overall reactivation rate constant of 1806 L mol-1 min-1. This means that K203 is a very potent reactivator of tabun-inhibited AChE. In addition, K203 reversibly inhibited AChE (K i = 0.090 mmol L-1) and BChE (K i = 0.91 mmol L-1), and exhibited its protective effect against phosphorylation of AChE by tabun in vitro. In vivo, a quarter of the LD50 K203 dose insured survival of all mice after the application of as many as 8 LD50 doses of tabun, which is the highest dosage obtained compared to K048 and TMB-4. Moreover, K203 showed high therapeutic potency in tabun-poisoned rats, preserving cholinesterase activity in rat plasma up to 60 min after poisoning. This therapeutic improvement obtained by K203 in tabun-poisoning places this oxime in the spotlight for further development.

Open access

Maja Katalinić, Nikolina Maček Hrvat, Jana Žďárová Karasová, Jan Misik and Zrinka Kovarik

Even if organophosphorus (OP) nerve agents were banned entirely, their presence would remain a problem as weapons of terror (like in Syria). Oxime antidotes currently used in medical practice still fall short of their therapeutic purpose, as they fail to fully restore the activity of cholinesterases, the main target for OPs. As orphan drugs, these antidotes are tested too seldom for anybody’s benefit. Over the last few decades, search for improved reactivators has reached new levels, but the translation of data obtained in vitro to in vivo application is still a problem that hinders efficient therapy. In this study, we tested the strengths and weaknesses of extrapolating pyridinium oxime antidotes reactivation efficiency from in vitro to in vivo application. Our results show that this extrapolation is possible with well-determined kinetic constants, but that it also largely depends on oxime circulation time and its tissue-specific distribution. This suggests that pharmacokinetic studies should be planned at the early stages of antidote development. Special attention should also be given to improving oxime distribution throughout the organism to overcome this major constraint in improving overall OP therapy.

Open access

Elsa Reiner, Zoran Radić and Vera Simeon-Rudolf

Mechanisms of Organophosphate Toxicity and Detoxication with Emphasis on Studies in Croatia

This review comprises studies on the mechanisms of toxicity and detoxication of organophosphorus (OP) compounds done in Croatia in different research areas. One area is the synthesis of antidotes against OP poisoning and their in vivo testing in experimental animals. In vitro studies included in this review focus on the mechanisms of reversible inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), protection of cholinesterases from inhibition by OPs, and reactivation of phosphylated cholinesterases. The third area comprises distribution profiles of BChE and paraoxonase (PON) phenotypes in selected population groups and the detection of OPs and metabolites in humans. Finally, methods are described for the detection of OP compounds in human blood and other media by means of cholinesterase inhibition.

Open access

Anita Bosak, Maja Katalinić and Zrinka Kovarik

Kolinesteraze: struktura, uloga, inhibicija

Acetilkolinesteraza (AChE; E.C. i butirilkolinesteraza (BChE; E.C. enzimi su koji se zbog svoje uloge u organizmu intenzivno istražuju unutar područja biomedicine i toksikologije. Iako strukturno homologni, ovi enzimi razlikuju se prema katalitičkoj aktivnosti, odnosno specifičnosti prema supstratima koje mogu hidrolizirati te selektivnosti za vezanje mnogih liganada. U ovom radu dan je pregled dosadašnjih istraživanja kolinesteraza i njihovih interakcija s ligandima i inhibitorima te su izdvojene aminokiseline aktivnog mjesta koje sudjeluju u tim interakcijama.

Open access

Horst Thiermann, Kai Kehe, Dirk Steinritz, John Mikler, Ira Hill, Thomas Zilker, Peter Eyer and Franz Worek

Red Blood Cell Acetylcholinesterase and Plasma Butyrylcholinesterase Status: Important Indicators for the Treatment of Patients Poisoned by Organophosphorus Compounds

Inhibition of acetylcholinesterase (AChE) is regarded as the primary toxic mechanism of organophosphorus compounds (OP). Therapeutic strategies are directed to antagonise overstimulation of muscarinic receptors with atropine and to reactivate inhibited AChE with oximes. Reactivation is crucial within the neuromuscular synapse, where atropine is ineffective, since peripheral neuromuscular block eventually leads to respiratory failure. Patients with OP intoxication have to be identified as early as possible.

During an international NBC-defence exercise anesthetised pigs were poisoned with sarin, followed by treatment with atropine and oxime. Blood samples were drawn and red blood cell (RBC)-AChE activity determined with a fielded test system on-site. Within a few minutes the poisoning was verified. After administration of HI-6, RBC-AChE activity increased rapidly. Blood samples were reanalysed in our laboratory in Munich. Almost identical course of the AChE activities was recorded by both systems.

The more comprehensive cholinesterase status was determined in Munich. Oxime administration can be stopped when AChE is aged completely, but has to be continued as long as poison is present in the body and reactivation is possible.

To aid the on-site physician in optimising diagnosis and treatment, a fielded test system should be available to allow rapid determination of the complete cholinesterase status.