ToxSci Advance Access published online on September 17, 2008
Toxicological Sciences, doi:10.1093/toxsci/kfn187
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In vitro effects of yessotoxin on a primary culture of rat cardiomyocytes
* Department of Materials and Natural Resources, University of Trieste, Via A. Valerio 6, 34127 Trieste, Italy
Department of Life Sciences, University of Trieste, Via A. Fleming 22 / Via L. Giorgieri 7, 34127 Trieste, Italy
Tama Laboratory, Japan Food Research Laboratories, 6-11-10, Nagayama, Tama-shi, Tokyo 206-0025, Japan
Corresponding author: Aurelia Tubaro, Department of Materials and Natural Resources, University of Trieste, Via A. Valerio 6, 34127 Trieste, Italy. Phone: +39-040-558 7910; fax: +39-040-558 3215; e-mail: tubaro{at}units.it
Received July 11, 2008; revision received August 26, 2008; accepted August 26, 2008
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Abstract |
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Oral administration of yessotoxin (YTX) has been reported to induce ultrastructural alterations in rodent cardiac muscle. To study its effects on various fundamental aspects of cardiac muscle cells activity, i.e. cell beating, Ca2+ and cAMP levels as well as cell vitality, a primary culture of rat cardiomyocytes was used. Patch-clamp recordings, Ca2+ imaging and cAMP assays were performed on cultured cardiomyocytes to characterize YTX effects on the cell beating frequency. MTT and sulforhodamine B (SRB) tests were carried out to determine its effect on cardiomyocytes viability.
Videoimaging techniques showed a time- and concentration-dependent reduction in the beating frequency after 1, 5 and 24 h incubation with YTX (0.1-1 µM). This effect was neither associated to the uncoupling between the membrane electrical activity and Ca2+ release from intracellular stores nor to the impairment of the mechanisms controlling the Ca2+ homeostasis. In addition, 1 µM YTX did not modify basal cyclic AMP levels in cardiomyocytes. MTT and SRB assays revealed that incubation of cardiomyocytes with YTX (0.01-1 µM; 24, 48 and 72 h) caused a decrease in cell viability in a concentration- and time-dependent way. This effect was still evident in cardiomyocytes exposed to YTX for 1, 5 and 24 h and cultured up to 72 h in YTX-free medium.
Our results demonstrate that, at nanomolar concentrations, a short incubation with YTX causes an inhibition of the beating activity and an irreversible reduction of viability of cardiac cells in vitro.
Key Words: Yessotoxin; cardiomyocytes; in vitro toxicity; calcium; cAMP.