Objective: This study was designed to investigate the cardioprotective effect of the novel lipophilic iron chelator salicylaldehyde isonicotinoyl hydrazone (SIH) against the oxidative stress exerted by H
2O
2 through the production of
![](/images/glyphs/BL9.GIF)
OH radical via the Fenton reaction and to compare them with those of the hydrophilic iron chelator deferoxamine (DFO) and the Na
+/H
+ exchange inhibitor methylisobutyl amiloride (MIA).
Methods: We used long-term cultures of spontaneously beating adult guinea-pig ventricular cardiomyocytes developed and characterized previously in our laboratory. We assessed their contractile activity by video-recording as well as the underlying Ca
i2+ transients by Fura 2 fluorescence. In some experiments we also recorded these functional parameters, plus the electrical activity (action potentials) in response to electrical stimulation via suction pipettes, in individual freshly isolated myocytes.
Results: Exposure of the regularly and synchronously beating cultured cardiomyocytes to 100 μM H
2O
2 initially caused a substantial prolongation of Ca
i2+ transients accompanied by an irregular contractile activity, then in contractile arrest and a severalfold increase in cytosolic [Ca
2+] that occurred, within 30 min of H
2O
2 application. Similar effects were also observed using freshly isolated cardiomyocytes. The latter effects were first accompanied by significant prolongation of the action potential duration (APD) with superimposed early afterdepolarizations followed by a second phase with a very fast decrease in APD, contractions, as well as Ca
i2+ transients and a third phase of inexcitability, contractile arrest, increased cytoplasmic [Ca
2+] and a final contracture. All these effects were irreversible in both types of preparations but they could be fully prevented by a 15-min preincubation with 200 μM SIH. Similar protective effects were observed with DFO, but in this case a much higher concentration had to be used (1 mM) and much longer (2 h) preincubation was needed. By contrast, 5 μM MIA failed to fully protect the cardiomyocytes, although a significant delay (10 min) of the effects of H
2O
2 was observed.
Conclusions: The data indicate that SIH provides a very powerful and very fast protection against the oxidative stress exerted by H
2O
2 presumably via the iron-mediated Fenton reaction producing hydroxyl radical (
![](/images/glyphs/BL9.GIF)
OH), whereas the protective effect of DFO is hindred by its very slow and rather limited intracellular entry, and the protection that MIA exerts via the inhibition of Na
+/H
+ exchange against H
2O
2 much less effective.