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|Type:||Artigo de periódico|
|Title:||An Unusual Presynaptic Action Of Bothrops Insularis Snake Venom Mediated By Phospholipase A2 Fraction|
|Abstract:||A phospholipase A2-contraining 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 A2 (PLA2) activity, was assayed on isolated neuromuscular preparations. In the mouse phrenic nerve- diaphragm incubated in Tyrode at 37°C, the PLA2 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°C, the PLA2 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°C) incubation prevented the neuromuscular effect from developing. These results suggest that the PLA2-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.|
|Citation:||Toxicon. , v. 36, n. 10, p. 1323 - 1332, 1998.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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