The effect of 2,5-di-(tert-butyl)-1,4-benzohydroquinone (TBQ) on intracellular Ca2+ handling in rat ventricular myocytes

2,5-Di-(tert-butyl)-1,4-benzohydroquinone (TBQ) is a reversible inhibitor of SERCA, potentially making it a useful tool to study the effects of SERCA inhibition in cardiac cells. However, it is unknown if TBQalso has effects on other components of ventricular Ca handling. The aim of these experiments was to characterise the effects of TBQon Ca handling in rat ventricular myocytes and assess its suitability as a specific inhibitor of SERCA. This was achieved by voltage clamp via perforated patch and [Ca2+]; measurement using Fluo-3 AM. TBQ produced a fully reversible, concentration dependent decrease in the rate of systolic Ca decay. 10 mu M TBQ decreased the amplitude of the systolic Ca transient by 48 +/- 5% and the rate of decay by 54+/-6%. SR Ca content was also reduced by 62+/-4%. However, 10 mu M TBQ also decreased the peak L-type Ca current by 23 7%. At higher concentrations (100 mu M), TBQ also activated an outward current with a current voltage relationship consistent with a potassium current. This outward current was abolished by Glibenclamide (100 mu M). These data show that TBQ can be used to reversibly inhibit SERCA. However, at concentrations that decrease SERCA activity, TBQ also decreases the L-type Ca current and (at higher concentrations) activates an outward current which appears to be an ATP dependent potassium current. We conclude that TBQ cannot be used as a specific inhibitor of SERCA in rat ventricular myocytes. (C) 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).