STIM1-Orai1 interaction mediated calcium influx activation contributes to cardiac contractility of insulin-resistant rats

Fig. 1. The effect of MetS, and BTP2 on intracellular Ca2+ parameters. A Representative Ca2+ transients. The effect of the BTP2 effect and Caffeine was also demonstrated. B Intracellular Ca2+ changes in resting-state C The peak amplitude of the fluorescences related to the global Ca2+ transients are given as F/F0 D The time to peak fluorescence (TP), E The half-decay time (DT50), and F The caffeine response (n = 22, and 24 cells for CON and MetS, respectively, *:p < 0.05 vs. Con; ε: p < 0.05 vs. MetS)

Fig. 2. SR Ca2+ leakage and effect of BTP2. A Representative line scan images from cells loaded with Fluo 3 B Peak intensity (F/F0) C Spark frequency (100 µm−1 s−1) D Full duration at half-maximum (FDHM) E Full width half maximum (FWHM) fluorescence changes. (The recording after BTP2 application was taken from the same cell without changing the line scan) (n = 25, and 30 cells for Con and MetS, respectively, *: p < 0.05 vs. Con, ε: p < 0.05 vs. MetS)

Fig. 3. Papillary muscle contraction in rat ventricular strips A Representative contraction curves recorded from papillary muscles B The net contraction that was recorded in electrically stimulated papillary muscle strips. (n = 4 each C Trace shows the preparation steps before SOCE measurement. The cells were first exposed to a Ca2+-free bath solution, containing various inhibitors (2 µM Thapsigargin (SERCA blocker), 10 µM verapamil (Ca2+ channel blocker), 10 mM TEA (K+ channel blocker), and 10 µM KB-R 7943 (Na+/Ca2+-exchanger blocker), and then caffeine (10 mM, 3 min intervals) was administered to empty SR/ER Ca2+ stores. At the end of 10 min, the fluorescence increase was calculated by switching to a bath solution containing Ca2+(1,8 mM) D Representative SOCE in rat left ventricular myocytes for control and MetS groups. E SOCE in rat left ventricular myocytes after SR Ca2+ depletion for the control, MetS, and MetS + BTP2 groups. Fluo3 AM dye was used for SOCE measurement. (n = 8,9,6 cells for CON, MetS, MetS + BTP2 respectively) (*: p < 0.05 vs. Con)

Fig. 4. Whole-cell patch-clamp recording of store-operated Ca2+ current in rat left ventricular myocytes. A Whole-cell patch-clamp current recorded in Con group B Whole-cell patch-clamp current recorded in MetS group [Black line: presence of Ca2+ (1.8 mM); Blue line: absence of Ca2+ (0 mM + 2 µM Thapsigargin + 10 µM verapamil + 10 µM KB-R 7943); Orange line: BTP2 added (selective SOCE blocker, 20 μM); Green line: SOCE current (ISOCE) (= Orange—Blue)] C Comparison of ISOCE current between Con (black) and MetS (orange) groups. D The calculated maximum current of ISOCE (− 110 mV) (n = 11, and 9 cells for Con and MetS, respectively *: p < 0.05 vs. Con)

Fig. 5. The mRNA and protein levels in isolated ventricular cardiomyocytes. A STIM1 and Orai1 protein levels B STIM1 and Orai1 mRNA expression levels (*:p < 0.05 vs. Con)