Gender-specific difference in cardiac ATP-sensitive K+ channels
Harri J. Ranki, PhD*,
Grant R. Budas, BSc*,
Russell M. Crawford, PhD* and
Aleksandar Jovanovi , MD, PhD* 
* Tayside Institute of Child Health, Ninewells Hospital & Medical School, University of Dundee, Dundee, Scotland, United Kingdom
Division of Cardiovascular Diseases, Department of Internal Medicine, Mayo Clinic, Mayo Foundation, Rochester, Minnesota, USA
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Figure 1 Kir6.2, SUR2A and Kir6.1 messenger RNA levels in male and female ventricular tissue as obtained by reverse transcription polymerase chain reaction (RT-PCR) methodology. (A to C) Reverse transcription polymerase chain reaction products obtained with Kir6.1, Kir6.2 and SUR2A-specific primers from male and female guinea pig hearts. An equal amount of total RNA was used for reverse transcription, as the RT-PCR GAPDH-gene specific primers yielded the similar levels of products in both groups tested. (A1 to C1) Graphs corresponding to RT-PCR products depicted in A to C. Bars represents mean ± SEM. *p < 0.05.
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Figure 2 ATP-sensitive K+ channels subunit levels in ventricular tissue from male and female guinea pigs. (A) Western blot of immunoprecipitate pellets from guinea pig membrane fraction with the anti-SUR2A and anti-Kir6.2 antibodies. Note single signals in both cases and no cross-reactivity with any other proteins. (B) Western blot of immunoprecipitate pellets from cardiac membrane fractions from male and female guinea pigs. Note a much stronger signal in female than in male animals.
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Figure 3 Pinacidil-evoked changes in membrane current in male and female cardiomyocytes. (A) Membrane currents evoked by identical families of 400 ms voltage pulses in a cell that was first maintained under control conditions and then exposed to 100 µM pinacidil for 2 min in male and female cardiomyocytes. (B) Currents recorded before and after applications of pinacidil (n = 7) were normalized to input capacitance, and the resultant data are plotted (mean) against membrane potential. Current densities for control and pinacidil-stimulated male and female cardiac cells were determined from the corresponding current-voltage relationship. The pinacidil-sensitive component of current is shown in C for cells in B and current density (D) at 80 mV. Each point/bar represents mean ± SEM (n = 7 for each). *p < 0.05.
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Figure 4 Single-channel properties of ATP-sensitive K+ channels (KATP) in male and female cardiomyocytes. (A) Continuous recording of KATP activity in membrane patch excised in ATP-free environment from male and female guinea pig cardiomyocytes. Dotted lines represent zero current level, and holding potential was –60 mV. Amplitude (B), open-time (C) and closed-time (D) histograms obtained from A, plotted with a bin width size of 100 µs and fitted by one exponential function. Results of data fitting are plotted as solid lines or closed circles (mean amplitude was 4.06 pA and 4.15 pA for male tissue and female tissue, respectively; mean open time was 1.74 ms and 1.93 ms for male tissue and female tissue, respectively; mean closed time was 0.27 ms and 0.25 ms for male tissue and female tissue, respectively).
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Figure 5 Ischemia-reperfusion-induced Ca2+ loading in male and female cardiomyocytes. Typical time course of Fura-2 fluorescence ratio (left and center panels) and average concentration of intracellular Ca2+ at rest and after ischemia-reperfusion (right panel) obtained with cardiomyocytes isolated from male and female guinea pigs. Bars represent mean ± SEM (n = 8 to 10). *p < 0.05 when compared with its own control (graph) or when compared with the same condition in the opposite gender (graph).
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Figure 6 Comparison of Kir6.2 and SUR2A messenger RNA levels. (A) Reverse transcription polymerase chain reaction products obtained with Kir6.2 and SUR2A-specific primers from guinea pig ventricular tissue (male) using different dilutions of the same complementary DNA (cDNA) pool. (B) cDNA concentration-bend intensity relationship from A. Band intensities at 1 µl for Kir6.2 and 3 µl for SUR2A were considered to represent 100% of maximum.
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