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|Type:||Artigo de periódico|
|Title:||An unusual presynaptic action of Bothrops insularis snake venom mediated by phospholipase A(2) fraction|
|Abstract:||A phospholipase A(2)-containing fraction was isolated from the venom of Bothrops insularis by a combination of gel filtration on Sephadex G-150 and ion exchange chromatography on DEAE-Sephadex, Peak IV of the latter chromatography containing all of the phospholipase A(2) (PLA(2)) activity, was assayed on isolated neuromuscular preparations. In the mouse phrenic nerve-diaphragm incubated in Tyrode at 37 degrees C, the PLA(2) fraction produced an initial increase in the twitch tension and in the frequency of the mepps, followed by a dose-dependent, irreversible blockade. The replacement of 1.8 mM Ca2+ by 4 mM Sr2+ Inhibited the neuromuscular blocking effect of the fraction. In the chick biventer cervicis preparation incubated with Krebs solution at 37 degrees C, the PLA(2) fraction induced blockade but did not affect the response to acetylcholine and K+, excluding the involvement of post-synaptic and direct muscular effects. A low temperature (18-22 degrees C) incubation prevented the neuromuscular effect from developing. These results suggest that the PLA(2)-containing fraction acts predominantly at presynaptic sites at the neuromuscular junction. This fraction also accounts for most of the pharmacological effects of the crude venom. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.|
|Editor:||Pergamon-elsevier Science Ltd|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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