Neuromuscular action of Bothrops lanceolatus (Fer de lance) venom and a caseinolytic fraction.
A protein capable of inducing neuromuscular blockade in avian preparations and of depolarizing mouse diaphragm muscle was isolated from Bothrops lanceolatus venom using gel filtration and ion-exchange chromatography. The purified protein was a single chain polypeptide with an estimated molecular mass of 27.5 kDa by SDS-PAGE and had caseinolytic activity (13.3 units/mg), but no phospholipase A(2). B.lanceolatus venom (50 micro g/ml) and the caseinolytic protein (20 micro g/ml) produced contracture and progressive irreversible blockade (50% in 25+/-5 min (SEM) and 45+/-15 min, respectively), in indirectly stimulated chick biventer cervicis preparations. The contractile responses to acetylcholine (ACh; 37 and 74 micro M, n=6) were inhibited by venom and the caseinolytic protein, whereas those to potassium (13.4mM, n=6) were not. Membrane resting potential measurements in mouse hemidiaphragm preparations showed that B.lanceolatus venom and the purified protein caused depolarization which was prevented by D-tubocurarine (14.6mM). The venom produced a slight increase in the amplitude and frequency of miniature end-plate potentials, but this effect was not seen with the purified fraction. These results suggest that the purified protein acts exclusively post-synaptically.
Lôbo de Araújo
Albetiza
A
Departamento de Farmacologia, Faculdade de Ciências Médicas, Universidade Estadual de Campinas (UNICAMP), CP 6111, 13083-970, SP, Campinas, Brazil. albetiza@fcm.unicamp.br
Donato
José Luiz
JL
Leite
Gildo Bernardo
GB
Prado-Franceschi
Júlia
J
Fontana
Marcos Dias
MD
Bon
Cassian
C
Rodrigues Simioni
Léa
L
D000818:Animals; D017837:Bothrops; D002364:Caseins / Q000378:metabolism; D002645:Chickens; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003435:Crotalid Venoms / Q000737:chemistry / Q000494:pharmacology*; D003964:Diaphragm / Q000187:drug effects / Q000503:physiopathology; D004591:Electrophoresis, Polyacrylamide Gel; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D009045:Motor Endplate / Q000187:drug effects / Q000503:physiopathology; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D019148:Neuromuscular Blockade; D009466:Neuromuscular Blocking Agents / Q000737:chemistry / Q000494:pharmacology*; D009469:Neuromuscular Junction / Q000187:drug effects* / Q000503:physiopathology; D010447:Peptide Hydrolases / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*
D002364:Caseins; D003435:Crotalid Venoms; D009466:Neuromuscular Blocking Agents; D010447:Peptide Hydrolases