Fig. 3.

In vivo β-adrenergic dose-response is blunted in TgcTnIP82S. A: representative Ntg (n = 6) and Tg (n = 5) pressure-volume (PV) loops at baseline (solid line) and at highest point of Iso dose-response (10, 20, 40, and 80 ng·kg⁻¹·min⁻¹) (dashed line). Notice on left, a leftward and upward shift of Ntg PV loop, typical of adequate contractile adrenergic response, whereas the right shows the failure of TgcTnIP82S to respond to β-adrenergic stimulation. LVP, left ventricular pressure; LVV, left ventricular volume; ESPVR, end-systolic PV relationship. B: mean results for Iso dose-response of maximal rate constant of pressure rise (dP/dt_max). TgcTnIP82S mice show a blunted dose-dependent augmentation of systolic function vs. Ntg. *P < 0.001 is for group interaction terms analysis by two-way ANOVA repeated measures (RM). C: change (Δ) in dP/dt_max. D: Δmaximal rate of pressure rise normalized to instantaneous pressure (dP/dt_max/IP). E: Δpeak negative dP/dt (dP/dt_min). F: Δisovolumetric relaxation constant (τ), which was calculated by logistic regression. G: myofilament from Ntg and TgcTnIP82S that were subject to Iso dose-response showed no difference in TnI phosphorylation of Ser23/24. H: myofilament preparations from Ntg and TgcTnIP82S that were subject to Iso dose-response were determined by Pro-Q staining (left) and normalized to total protein content, determined by Sypro Ruby (middle). Comparison of normalized phosphorylation levels expressed as ratio of ProQ/Sypro Ruby signals. Phosphorylaton pattern is not significantly different (right). MyBP-C, myosin-binding protein C; MLC, myosin light chain. Values are means ± SE.