Influence of temperature upon effects of crotoxin and gamma-irradiated crotoxin at rat neuromuscular transmission.
The influence of temperature upon the effects of crotoxin (CTX), from Crotalus durissus terrificus venom, and gamma-irradiated (60Co, 2000 Gy) crotoxin (iCTX) was studied in rat neuromuscular transmission 'in vitro'. Indirect twitches were evoked in the phrenic-diaphragm preparation by supramaximal strength pulses with a duration of 0.5 ms and frequency of 0.5 Hz. The phospholipase A(2) (PLA(2)) enzymatic activity of CTX and iCTX was assayed against phosphadityl choline in Triton X-100. At 27 degrees C, CTX (14 microg/ml) did not affect the amplitude of indirectly evoked twitches. However, at 37 degrees C, CTX induced a time-dependent blockade of the neuromuscular transmission that started at 90 min and was completed within 240 min. iCTX (14 microg/ml) was inneffective on the neuromuscular transmission either at 27 or 37 degrees C. The PLA(2) enzymatic activity of CTX at 37 degrees C was 84 and that at 27 degrees C was 27 micromol fatty acid released/min/mg protein, and that of the iCTX at 37 degrees C was 39 micromol fatty acid released/min/mg protein. Thus, it was concluded that the mechanism of detoxification of CTX by gamma radiation at the neuromuscular level relies on the loss of its PLA(2) enzymatic activity.
Gallacci
M
M
Departamento de Farmacologia, Instituto de Biociências-UNESP, Universidade Estadual Paulista, Rubião Júnior, Botucatu, São Paulo, Brazil. gallacci@ibb.unesp.br
Nascimento
N
N
Rogero
J R
JR
Vassilieff
V S
VS
D000818:Animals; D003439:Crotoxin / Q000528:radiation effects* / Q000633:toxicity*; D003964:Diaphragm / Q000187:drug effects* / Q000294:innervation; D004789:Enzyme Activation / Q000528:radiation effects; D005720:Gamma Rays; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009469:Neuromuscular Junction / Q000187:drug effects*; D010741:Phospholipases A / Q000378:metabolism / Q000528:radiation effects; D010791:Phrenic Nerve / Q000187:drug effects / Q000502:physiology; D051381:Rats; D009435:Synaptic Transmission / Q000187:drug effects*; D013696:Temperature
D003439:Crotoxin; D010741:Phospholipases A