Ação do veneno total de Bothrops pirajai e de suas frações miotoxicas piratoxinas I e III sobre a musculatura esqueletica : estudos in vitro

AUTOR(ES)
DATA DE PUBLICAÇÃO

1999

RESUMO

Several reasons can be cited which motivate the study of natural substances such as the characterization of the active principles and its biological effects. Among them, the ophidic venoms stand out because it is common the occurrence of accidental envenomation after snake bites in tropical countries. In Brazil, ophidic accidents account for a major part in the context of Public Health were the genus Bothrops is responsable for about 90% of them. Myonecrosis is one ofthe local effects whose rapid onset is difficult to control and deserves special attention in the treatment approaches after envenomation. Myonecrosis is triggred by myotoxic proteins specifical1y acting in muscle fibers at the bite site. Due to the scarcity of studies about the biological actions of Bothrops pirajai (li jararacussu of Bahia") snake venom, arare and exclusive specimen living in Bahia and northeastrn of Minas Gerais, the present work was proposed viewing to investigate miotoxic and neurotoxic activities of crude venom and its fractions Piratoxin-I (PrTX-I) and Piratoxin-III (PrTX-III). The studies were performed in mice isolated muscle preparations of the extensor digitorum longus (EDL) and phrenic nerve-diaphragm (PND) muscles through myographic, histological and ultrastructural analysis and determination of creatinokinase (CK) in the incubation bath. The venom and the fraction PrTX-III (10, 25 and 50 µg/ml) caused a dose-dependent twitch-tension blockade of the EDL muscle fibers, histological and ultrastructural changes of muscle cells and nerve endings culminating in complete necrosis of both and increased CK release in the bath. PrTX-I caused a dose dependent blockade (5, 10 and 20 µg/ml) onhe twitch tension in PND muscle fibers and severe myonecrosis. However, PrTX-I did not affect muscle fibers nor caused alter(!.tions on the twitch tension responses in EDL. These differences could be accounted for a distinct sensitivity of EDL and PND muscle fibers to the venom and PrTX-I possibly related to the amount of slow- and fast-contracting fibers present in each one. Our results suggest that PrTX-I and PrTX-III of B. pirajai venom would be the components accounting for the myotoxic activity of venom despite a distinct mechanism of action could be implied. Additionally, these preliminary results suggest a potent neurotoxic activity, also observed with the whole venom

ASSUNTO(S)

cobra venenosa - venenos - efeito fisiologico microscopia eletronica junção neuromuscular

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