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|Type:||Artigo de periódico|
|Title:||Pharmacological study of a new Asp49 phospholipase A(2) (Bbil-TX) isolated from Bothriopsis bilineata smargadina (forest viper) venom in vertebrate neuromuscular preparations|
de Abreu, VA
da Cruz-Hofling, MA
|Abstract:||The neuromuscular activity of Bbil-TX, a PLA(2) with catalytic activity isolated from Bothriopsis bilineata smargadina venom, was examined in chick biventer cervicis (BC) and mouse phrenic nerve-diaphragm (PND) preparations. In BC preparations, Bbil-TX (0.5-10 mu g/ml) caused time- and concentration-dependent blockade that was not reversed by washing; the times for 50% blockade were 87 +/- 7, 41 +/- 7 and 19 +/- 2 min (mean +/- SEM; n = 4-6) for 1, 5 and 10 mu g/ml, respectively. Muscle contractures to exogenous ACh and KCl were unaffected. The toxin (10 mu g/ml) also did not affect the twitch-tension of directly-stimulated, curarized (10 mu g/ml) BC preparations. However, Bbil-TX (10 mu g/ml) produced mild morphological alterations (edematous and/or hyperchromic fibers) in BC; there was also a progressive release of CK (from 116 +/- 17 IU/ml (basal) to 710 +/- 91 IU/ml after 45 min). Bbil-TX (5 mu g/ml)-induced blockade was markedly inhibited at 22-24 degrees C and pretreatment with p-bromophenacyl bromide (p-BPB) abolished the neuromuscular blockade. Bbil-TX (3-30 mu g/ml, n = 4-6) caused partial time- and concentration-dependent blockade in PND preparations (52 +/- 2% at the highest concentration). Bbil-TX (30. mu g/ml) also markedly reduced the MEPPs frequency [from 26 +/- 2.5 (basal) to 10 1 after 60 min; n = 5; p < 0.05] and the quantal content [from 94 +/- 14 (basal) to 24 +/- 3 after 60 min; n = 5; p < 0.05] of PND preparations, but caused only minor depolarization of the membrane resting potential [from -80 +/- 1 my (basal) to -66 +/- 2 mV after 120 min; n = 5; p < 0.05], with no significant change in the depolarizing response to exogenous carbachol. These results show that Bbil-TX is a presynaptic PLA(2) that contributes to the neuromuscular blockade caused by B. b. smargadina venom. (C) 2013 Elsevier Ltd. All rights reserved.|
Bothriopsis bilineata smargadina
|Editor:||Pergamon-elsevier Science Ltd|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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