Intravenous paraoxon (POX) exposure: coagulation studies in mini pigs

The in vivo effects of the organophosphorus compound (OPC) paraoxon (POX) o n blood coagulation of mini pigs were assessed by measuring the partial thr omboplastin time (PTT), prothrombin time (PT), fibrinogen, factor V, factor VII, factor VIII, antithrombin III, protein C, and platelet count. The min i pigs were randomly assigned to a POX-treatment group (n = 9) receiving 54 mg POX kg(-1)BW(-1) or the control group (n = 9). Measurements were carrie d out over a period of 150 min after poisoning. The exposure to POX did not have any influence on measurements of PT, factor VIII, factor VII, factor V, antithrombin III, protein C, or fibrinogen compared to the control group evaluated by rank order lest (ROT) during the time of observation (150 min ). Changes seen in the intrinsic coagulation followed a biphasic pattern co rresponding to an early sympathomimetic phase with PTT-shortening and a dec rease of the platelet count, and a late vagal phase, with PTT-prolongation. The hypercoagulability seen in the sympathomimetic phase is probably due t o a massive release of catecholamines from the adrenals. Previous studies s howed in vitro no coagulation activating effect of POX. The hypocoagulabili ty in the vagal phase shown by the PTT-prolongation is probably due to POX influencing platelet function or its inhibition of clotting factors, which are serine proteases, or a combination of the two. (C) 1999 Elsevier Scienc e Ireland Ltd. All rights reserved.