Functional characterization of a basic D49 phospholipase A2 (LmTX-I) from the venom of the snake Lachesis muta muta (bushmaster).
The whole venom of Lachesis muta muta is preponderantly neurotoxic but moderately myotoxic on the chick biventer cervicis preparation (BCp). We have now examined these toxic activities of a basic phospholipase A(2), LmTX-I, isolated from the whole venom. LmTX-I caused a significant concentration-dependent neuromuscular blockade in the BCp. The time to produce 50% neuromuscular blockade was 14.7+/-0.75 min (30 microg/ml), 23.6+/-0.9 min (10 microg/ml), 34+/-1.7 min (2.5 microg/ml) and 39.2+/-3.6 min (1 microg/ml), (n=5/concentration; p<0.05). Complete blockade with all tested concentrations was not accompanied by inhibition of the response to ACh. At the highest concentration, LmTX-I (30 microg/ml) significantly reduced contractures elicited by exogenous KCl (20mM), increased the release of creatine kinase (1542.5+/-183.9 IU/L vs 442.7+/-39.8 IU/L for controls after 120 min, p<0.05), and induced the appearance of degenerating muscle fibers ( approximately 15%). Quantification of myonecrosis indicated 14.8+/-0.8 and 2.0+/-0.4%, with 30 and 10 microg/mlvenom concentration, respectively, against 1.07+/-0.4% for control preparations. The findings indicate that the basic PLA(2) present on venom from L. m. muta (LmTX-I) possesses a dominant neurotoxic action on isolated chick nerve-muscle preparations, whereas myotoxicity was mainly observed at the highest concentration used (30 microg/ml). These effects of LmTX-I closely reproduce the effects of the whole venom of L. m. muta in chick neuromuscular preparations.
Damico
Daniela C S
DC
Departamento de Bioquímica, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), P.O. Box 6109, Campinas, SP, Brazil.
Bueno
Lilian G F
LG
Rodrigues-Simioni
Léa
L
Marangoni
Sérgio
S
da Cruz-Höfling
Maria Alice
MA
Novello
José Camillo
JC
D000109:Acetylcholine; D000818:Animals; D002645:Chickens; D003435:Crotalid Venoms / Q000737:chemistry / Q000201:enzymology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects / Q000473:pathology; D009466:Neuromuscular Blocking Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D010741:Phospholipases A / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D054467:Phospholipases A2; D011189:Potassium Chloride; D017819:Viperidae / Q000502:physiology*
D003435:Crotalid Venoms; C072644:Lachesis venom; D009466:Neuromuscular Blocking Agents; D011189:Potassium Chloride; D010741:Phospholipases A; D054467:Phospholipases A2; D000109:Acetylcholine