Abstract 12404: Cardioprotective Diazoxide Inhibits Succinate Dehydrogenase Independent of the Adenosine Triphosphate Sensitive Potassium Channel in Mouse and Human Mitochondria
Introduction: Adenosine triphosphate sensitive potassium channel (KATP) opener diazoxide provides cardioprotection during myocyte stress via an unknown mechanism that has been proposed to involve the inhibition of succinate dehydrogenase and the activation of a mitochondrial KATP channel (mKATP). Diazoxide’s cardioprotection is eliminated by the prevention of its ability to inhibit succinate dehydrogenase (SDH) and by genetic deletion of KATP channel subunit SUR1. Interestingly, diazoxide still inhibits SDH in SUR1 deficient mice, suggesting the inhibition of SDH precedes mKATP activation; however, the relationship between the succinate dehydrogenase enzyme complex and a mitochondrial KATP channel are unknown.
Hypothesis: We hypothesized that the addition of mKATP channel inhibitor, 5 - hydroxydecanoate (5-HD), would alter diazoxide’s ability to inhibit SDH.
Methods: Mitochondria were isolated from mouse hearts and human left ventricular specimens using serial homogenization and exposed to test groups: 8 mM malonate (inhibitor of SDH), 100 microM diazoxide (DZX), 100 microM 5-HD, DZX + 5 HD, succinate control, no succinate, and no mitochondria. SDH activity was measured by spectophotometric analysis fo 2-6 dicholoroindophenol reduction at 600nm for 20 min.
Results: Diazoxide inhibited SDH in mouse and human mitochondria (figure demonstrates human SDH activity, percent change in absorbance is inversely proportional to SDH activity) (*p<0.05 vs. succinate control). However, SDH activity was not altered by the addition of 5-HD (DZX + 5-HD not significantly different from DZX alone).
Conclusions: Similar to previous results following genetic deletion of mKATP subunit SUR1, these data are consistent with the inhibition of SDH by diazoxide as upstream to mKATP activation as diazoxide inhibits SDH despite the inhibition of mKATP by 5 - HD.
Author Disclosures: M.B. Janjua: None. E.M. Kanter: None. C.M. Makepeace: None. M.C. Henn: None. R.B. Schuessler: None. C.G. Nichols: None. J.S. Lawton: None.
- © 2014 by American Heart Association, Inc.