Figure 3.

In vivo assessment of LV contractile function. Measured parameters are shown at baseline and after progressive injections of isoproterenol. Hemodynamic measurements were performed in transgenic mice overexpressing the CAM β₂-adrenergic receptor (A and B: ICI 118,551 treated, n = 11; vehicle treated, n = 10) and nontransgenic littermate controls (C and D: ICI 118,551 treated, n = 11; vehicle treated, n = 9). Data are expressed as mean ± SEM. ICI 118,551-treated vs. vehicle-treated data were compared using a two-way repeated-measure ANOVA. Post-hoc comparison of differences in mean values between the groups at a specific dose were conducted with a Newman–Keuls test; ∗, P < 0.01. A significant between-group main effect in response to isoproterenol was found for LV dP/dtmax (A; P < 0.05). The pattern of change between groups was statistically different for LV dP/dtmax (A; P < 0.0001) and LV systolic pressure (B; P < 0.05). ICI 118,551 treatment of animals did not alter the measured hemodynamic parameters in nontransgenic littermate controls (C and D). LV end diastolic pressure was not statistically different between groups at baseline (4.4 ± 0.8 vs. 5.3 ± 0.6 mmHg in ICI 118,551-treated vs. vehicle-treated transgenic animals, respectively; 4.9 ± 0.6 vs. 4.0 ± 0.7 mmHg in ICI 118,551-treated vs. vehicle-treated littermate controls, respectively). Pretreatment with ICI 118,551 did not alter heart rate in transgenic mice (484 ± 33 vs. 525 ± 24 beats per min mmHg in ICI 118,551-treated vs. vehicle-treated animals, P = ns), or in nontransgenic littermate controls (383 ± 21 vs. 370 ± 25 beats per min in ICI 118,551-treated vs. vehicle-treated animals, P = ns).