Neutralizing capacity of commercial bothropic antivenom against Bothrops jararacussu venom and bothropstoxin-I

Bothrops jararacussu venom and its major toxin, bothrops-toxin-I (BthTX-I), possess myotoxic and neurotoxic activities. The ability of commercial equi ne antivenom to neutralize these activities was studied in mouse isolated p hrenic nerve-diaphragm (PND) and extensor digitorum longus (EDL) preparatio ns by indirect stimulation (0.1 Hz, 0.2 ms). The time required to produce 5 0% neuromuscular blockade in the PND and EDL preparations was, respectively , 70 +/- 11.5 min and 58 +/- 8 min for B. jararacussu venom (50 mug/mL), an d 31 +/- 6 min and 30 +/- 3 min for BthTX-I (20 mug/mL). After a 120-min in cubation, the creatine kinase (CK) concentrations in the EDL preparations w ere 3464 +/- 346 U/L and 3422 +/- 135 U/L following exposure to venom (50 m ug/mL) and BthTX-I (20 mug/mL), respectively. Antivenom neutralized the neu romuscular blockade induced by the venom and toxin in PND preparations in a dose-dependent fashion, but only partially neutralized this effect in EDL. Antivenom also effectively prevented the venom- and toxin-induced release of CK from EDL. In contrast, histological analysis showed that the morpholo gical damage caused by a. jararacussu Venom and BthTX-I in the EDL was only partially prevented by the antivenom. These results indicate that commerci al equine antiserum fully protects against the neurotoxic action of B. jara racussu and BthTX-I in PND preparations, but only partially protects agains t the neurotoxic and myotoxic actions of the venom and its toxin in EDL pre parations. Care must therefore be exercized in extrapolating results from d ifferent preparations even when similar pharmacological or physiological re sponses are involved. (C) 2000 John Wiley & Sons, Inc.