Chemical and functional analyses of Rhinella icterica (Spix, 1824) toad secretion screened on contractions of the heart and oviduct in Locusta migratoria.

J Insect Physiol

Laboratório de Neurobiologia e Toxinologia (LANETOX), Programa de Pós-Graduação em Ciências Biológicas (PPGCB), Universidade Federal do Pampa (UNIPAMPA), São Gabriel, RS, Brazil; Programa de Pós-Graduação em Ciências Biológicas: Bioquímica Toxicológica (PPGBTox), Universidade Federal de Santa Maria (UFSM), Santa Maria, RS, Brazil. Electronic address:

Published: September 2021

AI Article Synopsis

  • Rhinella icterica is a Brazilian toad with a toxic secretion that is effective against insects, specifically studied using locust heart and oviduct preparations.
  • The secretion causes various effects such as negative chronotropism in the heart and increased muscle contraction in the oviduct, suggesting different sensitivities to the secretion's components.
  • Chemical analysis of the secretion revealed several compounds, highlighting that bufadienolides may mediate the observed effects in oviduct muscle, while no phospholipase A activity was found.

Article Abstract

Rhinella icterica is a Brazilian toad with a parotoid secretion that is toxic to insects. In this work, we examined the entomotoxicity of this secretion in locust (Locusta migratoria) semi-isolated heart and oviduct preparations in vitro. The parotoid secretion caused negative chronotropism in semi-isolated heart preparations (at the highest dose tested: 500 μg) and markedly enhanced the amplitude of spontaneous contractions and tonus of oviduct muscle (0.001-100 μg). In addition, the secretion enhanced neurally-evoked contractions of oviduct muscle, which was more sensitive to low concentrations of secretion than the semi-isolated heart. The highest dose of secretion (100 μg) caused neuromuscular blockade. In zero calcium-high magnesium saline, the secretion still enhanced muscle tonus, suggesting the release of intracellular calcium to stimulate contraction. Reverse-phase HPLC of the secretion yielded eight fractions, of which only fractions 4 and 5 affected oviduct muscle tonus and neurally-evoked contractions. No phospholipase A activity was detected in the secretion or its chromatographic fractions. The analysis of fractions 4 and 5 by LC-DAD-MS/MS revealed the following chemical compounds: suberoyl arginine, hellebrigenin, hellebrigenin 3-suberoyl arginine ester, marinobufagin 3-pimeloyl arginine ester, telocinobufagin 3-suberoyl arginine ester, marinobufagin 3-suberoyl arginine ester, bufalin 3-adipoyl arginine, marinobufagin, bufotalinin, and bufalitoxin. These findings indicate that R. icterica parotoid secretion is active in both of the preparations examined, with the activity in oviduct possibly being mediated by bufadienolides.

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http://dx.doi.org/10.1016/j.jinsphys.2021.104192DOI Listing

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