engleski

Cholinesterases activity and oxidative stress in rats upon tabun poisoning and oxime therapy

Rats have been used in study of temporal distribution of the cholinesterase activity after exposure to tabun and treatment with oxime 1-(4-hydroxyiminomethylpyridinium)-4-(4-carbamoylpyridinium) butane dibromide, K048. In the event of poisoning by organophosphorus compounds (OP), immediate therapeutic treatment usually consists of combined administration of an anticholinergic drug, such as atropine, and an oxime-reactivator of acetylcholinesterase. However, the treatment is very limiting in case of nerve agent tabun poisoning. Since our recent in vitro and in vivo studies on mice showed that oxime 1-(4-hydroxyiminomethylpyridinium)-4-(4-carbamoylpyridinium) butane dibromide (K048) is very promising as reactivator of tabun-inhibited human erythrocyte acetylcholinesterase and as antidote of tabun poisoned mice, we tested antidotal potency of K048 in tabun-poisoned rats. We measured acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activity in plasma after 0.5, 1, 6 and 24 h long oxime therapy. In view of the possible oxidative stress involved in OP poisoning, it has been decided to estimate the levels of oxidative stress (lipid peroxidation), and to see whether any difference exists in this parameter upon tabun poisoning and administrated therapy in rats. Male rats received a subcutaneous (s.c.) dose of 3/4 of the tabun LD50. Oxime was given intraperitoneally (i.p.) at doses of 1/4 of its LD50 after 1 min of tabun poisoning. Animals were divided into 5 groups of four animals receiving: tabun (I), oxime (II), atropine (III) tabun+oxime+atropine (IV) and saline as control group. Atropine was administered i.p. (10.0 mg/kg body weight) together with oxime. All animals were sacrificed after 0.5, 1, 6 and 24 h. Plasma was diluted 50 times for AChE and BChE activity measurement by Ellman assay at 25 °C using acetylthiocholine as substrate. AChE and BChE activity was determined using selective inhibitors BW284C51 and ethopropazine, respectively. As a measure of lipid peroxidation the concentration of thiobarbituric reactive substances (TBARS) was determined using modification of the method by Drury et al. (1997). Activity of AChE and BChE (control group and group II) ranged from 1.5-2.9 and 0.6-1.8  mol min-1 per g of protein, respectively, with no matter of sacrifice time. Activity of group I and III of both enzymes was below 0.3  mol min-1 per g of protein up to 6 h, while in 24 h both activities were completely restored. AChE activity of group IV in 30 min and 1 h was in same range as control confirming the K048 reactivation potency, while in 6 h the therapy by K048 was depleted - AChE activity was low as in group I. Treatment with K048 did not preserve BChE activity that is also in accordance with previous K048 in vitro study, due to limiting BChE reactivation by K048. The levels of plasma TBARS progressively increased up to 6 h for all treatment groups. The major increase was detected after tabun administration while only minor time-dependent differences were observed after treatment with K048. Although the levels of TBARS decreased up to 24 h, they remained above the range of the control for most of the treatments. The significant improvement was noticed in the AChE activity of tabun-poisoned rats with applied K048 therapy. Poisoning did not significantly induce the oxidative stress.

tabun ; oxime ; therapy ; cholinesterases ; acetylcholinesterase ; butyrylcholinesterase ; in vivo ; K048 ; oxidative stress ; TBRS

DOI: 10.1007/s12031-009-9277-5