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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
NEUROMUSCULAR BLOCKADE INDUCED BY JACK BEAN UREASE IN
NAUPHOETA CINEREA COCKROACHES
Authors: Santos, D.S 1,2, Zanatta, A. P 2, Almeida, C.G.M 2,4, Perin, A.P2, Freitas, T.C
3
, Heberle, M.A 2, Vinadé, L 2., Pinto, P.M 2, Carlini, C.R 3,4, Dal Belo, C. A 1,2.
1
PPGBTox, Universidade Federal de Santa Maria, UFSM, Santa Maria, Brazil.
2
LANETOX, Universidade Federal do Pampa, UNIPAMPA, São Gabriel, Brazil;
3
PPGBCM, Universidade Federal do Rio Grande do Sul, UFRGS, Porto Alegre, Brazil;
4
LaNeurototox, Brain Institute, Pontificia Universidade Católica do Rio Grande do Sul,
Porto Alegre, Brazil
Key words: Canavalia ensiformis, Acetylcholinesterase, Neuromuscular blockade.
The entomotoxic activity of jack bean urease (JBU) has been proved but its exact
mechanism of action is still uncertain. The aim of this work was to investigate the
anticholinesterase and neuromuscular activities of JBU in vivo on Nauphoeta cinerea.
Cockroaches of both sexes were maintained with water and dog chow ad libitum (2326°C). Cockroach metathoracic coxal-adductor nerve-muscle preparation was mounted
as in Martinelli (2014). Cockroach brain acetylcholinesterase (AChE) activity was
measured according to Sturmer (2014). Treatments were administered at cockroach
third abdominal segment (10 µl/animal). Data were expressed as mean ± S.E.M.
Differences were validated by ANOVA/MANOVA or Student t test with p<0.05 indicating
significance. In control-saline protocols there was no alteration of physiological muscle
twitch tension in 120min recordings (n=6). The assays with JBU (1.5, 3 and 6μg/g
animal) showed a time-dependent neuromuscular blockade, in 120min recordings. With
1.5μg/g JBU, there was 30± 0% blockage of muscle twitches (n=6, p<0.05). The assay
of JBU 3μg/g induced only 15±4% inhibition of the muscle twitch tension (n=6, p<0.05).
However, JBU 6μg/g induced 70±7% depression in the muscle strength (n=6, p<0.05).
In this set of protocols the pretreatment of animals with bicuculine (5µg/g) prevented
40% the neuromuscular blockade induced by 6μg/g JBU (n=6, p<0.05). The control
value for insect brain AChE activity was 186 ± 3 nmol NADPH/min/mg protein (n=3).
After treatment with different concentrations of JBU (1.5, 3 and 6μg/g animal), there was
a decrease in the enzyme activity to 125.5±6, 125.5±3 and 73.5±5nmol TNB/min/mg
protein, respectively (n=3; p<0.05). The data suggest that the entomotoxic activity of
Jack Bean Urease involves peripheral neurotoxicity, mostly by altering GABA
neurotransmission. The inhibition of AChE may play a parallel and synergic effect in the
overall urease toxicity in the insects.
Acknowledgements: CAPES Fellowship, Edital Toxinologia CAPES 063/2010.
Brazilian Society for Biochemistry and
Molecular Biology (SBBq)