Skip to main content
. Author manuscript; available in PMC: 2017 Jan 5.
Published in final edited form as: Circulation. 2015 Dec 1;133(1):48–61. doi: 10.1161/CIRCULATIONAHA.115.017472

Figure 3.

Figure 3

Impaired βAR agonist-induced cardiac contractile function and blunted calcium coupling in STAT3-deficient hearts and cardiomyocytes. A–C, Evaluation of acute inotropic (A), lusitropic (B) responses, and LV developed pressure (LVDP) (C) in Stat3cKO and control hearts in response to dobutamine stimulation using a Langendorff perfusion system. Dobutamine was infused for 20 minutes. (bw: body weight ; Mean ± SEM; N=6/each group; *p<0.01 and **p<0.001). D, Western blots show that the levels of phosphorylated troponin I and phospholamban (PLB) are reduced in Stat3cKO hearts when compared to controls after 30 minutes of dobutamine stimulation. E, cAMP levels in Stat3cKO hearts are significantly lower compared to controls treated with dobutamine stimulation (N = 3/each group; *p<0.05). F–G, Comparison of steady-state Ca2+ transients from control and Stat3cKO cardiomyocytes. Prior to dobutamine treatment, Ca2+ transient amplitudes (F) and Tpeak (activation kinetics) (G) are comparable in control and Stat3cKO cardiomyocytes. (Control: N = 17 cells/4 mice; Stat3cKO: N = 17 cells/3 mice). Dobutamine stimulation increases the amplitude and speeds the kinetics (Tpeak) of control cardiomyocytes. In contrast, the amplitude and Tpeak of Ca2+ transient in Stat3cKO cells are not affected by dobutamine stimulation. H, Assessment of SR Ca2+ content of control and Stat3cKO ventricular cardiomyocytes. Prior to dobutamine treatment, SR Ca2+ content is similar between control and Stat3cKO ventricular myocytes. In response to dobutamine treatment, SR Ca2+ content is increased in control, but not in Stat3cKO cardiomyocytes (Control: N = 15 cells/3 mice; Stat3cKO: N = 18 cells/3 mice). I, Measurement of spontaneous Ca2+ spark frequency in control and Stat3cKO ventricular cardiomyocytes. Prior to dobutamine treatment, Ca2+ spark frequency is comparable in control and Stat3cKO cardiomyocytes. In response to dobutamine treatment, Ca2+spark frequency increases significantly in control cells, but not in Stat3cKO cells. (Control: N = 20 cells/3 mice; Stat3cKO: N = 21 cells/3 mice). *P<0.05, **P<0.01.