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23 Congress of the International Union for Biochemistry and Molecular Biology
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44 Annual Meeting of the Brazilian Society for Biochemistry and Molecular Biology
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Foz do Iguaçu, PR, Brazil, August 24 to 28 , 2015
ENTOMOTOXIC ACTIVITY IN VENOM OF TOAD Rhinella icterica (ANURA:
BUFONIDAE)
Authors: Leal, A. P.¹, Pesamosca, M. E.¹, Oliveira,R.S¹, POSSER, Thais³, Franco, J. L³,
Vinadé, L.¹, Santos, T. G. dos.², Dal Belo, C. A.¹
¹LANETOX (Laboratório de Neurobiologia e Toxinologia); ²LEBIP (Laboratório de
Estudos em Biodiversidade Pampiana), ³Grupo de Pesquisa em Estresse Oxidativo e
Sinalização Celular. Universidade Federal do Pampa, São Gabriel, Brazil.
Key words: Toad venom, Rhinella icterica, natural insecticide, cardiotoxicity,
neuromuscular blockade, acetylcholinesterase inhibition.
Toad venoms are wealth sources for peptides with potential biotecnological interest. In
this work we have investigated the mechanisms involved in the entomotoxic activity
induced by R. icterica toad venom (RITV). For the assessement of RITV entomotoxic
activity, one hundred flyes (Drosophila melanogaster) were allocated in a glass flasks
containing a filter paper soaked with RITV diluted in 2 M sacarose. The analysis of in
vitro RITV inhibition of AChE was evaluated according to Ellman (1961), with
modification by Franco (2009). Cardiotoxicity was evaluated in cockroach semi-isolated
heart preparation, as described by Rodrigues (2012). The neuromuscular activity of
RITV was evaluated using in vivo metathoracic coxal-adductor nerve-muscle
preparation (MCAP) according to Martinelli (2014). After 24h exposition to RIVT
(1000g/mL), a number of 503 flies were accounted as dead, meaning the LD50
(p<0.05, n=3). Incubation of RITV (1, 2 and 3g.l-1), induced a dose-dependent
inhibition cockroach brain homogenate AchE activity (n=3). The addition of RIVT (1, 2, 4
and 8g.g-1) at cockroach semi-isolated heart preparation induced a concentration and
time-dependent decrease in the heart rate, that was maximum (504 beats.min-1) for
the highest dose in 30 min incubation (n=6, p<0.05). The washout of the preparations
with insect saline was ineffective to reverse the negative chronotropic activity. The
recordings of MCAP in cockroaches treated with RIVT (10, 25, and 50g/animal)
showed a dose and time dependent progressive decrease in the muscle twitches (n=3,
respectively). Thus, when RTIV (50g/animal) was administrated there was a maximum
and complete neuromuscular blockade, in 120min recordings (n=3, p<0.05). In
conclusion, RITV presented insecticide activity, which may be related to a peripheral
neurotoxicity in parallel to the cardiotoxic activity. The anticholinesterase effect may play
a secondary toxicicity in cockroaches. The biological activity of RITV in insects indicates
the presence of o neurotoxins with biotecnological interest.
Brazilian Society for Biochemistry and
Molecular Biology (SBBq)