Neuromuscular and phospholipase activities of venoms from three subspeciesof Bothrops neuwiedi (B. n. goyazensis, B. n. paranaensis and B. n. diporus)

ABSTRACT

The Bothrops neuwiedi (Neuwied's lancehead) species complex consists of a variety of subspecies with a wide distribution in South America. Inthis work, we compared the neuromuscular blockade caused by venoms from three subspecies (B. n. goyazensis, B. n. paranaensis and B. n. diporus)of this complex using chick biventer cervicis (BC) and mouse phrenic nerve-diaphragm (PND) preparations and investigated their phospholipaseA2 (PLA2) activities and electrophoretic profiles. The order of potency of PLA2 activity was B. n. diporusNB. n. paranaensisNB. n. goyazensis. InBC preparations, B. n. goyazensis venom (50 ìg/mL) was significantly (pb0.05) more active than B. n. paranaensis and B. n. diporus venoms,which did not produce a significant blockade at this time interval; after 120 min, B. n. goyazensis, B. n. paranaensis and B. n. diporus venoms(100 ìg/mL) produced blockades of 57.4±5%, 30±3% and 17.4±7% (n=3–6 each), respectively. The three venoms inhibited contractures inresponse to ACh, indicating interference with postsynaptic neurotransmission. Only B. n. goyazensis and B. n. paranaensis venoms caused a longlasting,concentration-dependent muscle contracture prior to blockade. In PND preparations, all of the venoms blocked the twitch-tension responseswithin 45–100 min, indicating that these preparations were more sensitive than avian preparations. There was a correlation between PLA2 activityand the time for 50% blockade in PND but not in BC preparations. SDS-PAGE showed quantitative rather than qualitative differences among thevenoms. These results indicate that the venoms of the three subspecies had similar profiles of neuromuscular activity, although the relationship withPLA2 activity varied with the preparation used.