Abnormal Cardiac Response to Physiologic Stress in PGC-1α^−/− Mice

<div><p>(A) Exercise echocardiographic studies. PGC-1α^+/+ (<i>n</i> = 4) and PGC-1α^−/− (<i>n</i> = 8) female mice aged 6–8 mo were subjected to an exercise protocol on a motorized treadmill. This protocol was designed such that the PGC-1α^−/− mice ran to exhaustion based on the results of the exercise studies shown in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0030101#pbio-0030101-g004" target="_blank">Figure 4</a>. Accordingly, an exercise regimen of 60 s was used for both groups. The graphs depict the heart rate (left graph) and echocardiographically-determined ventricular fractional shortening (FS) as a percent (right graph). Responses were monitored for 10 min immediately post exercise.</p> <p>(B) In vivo hemodynamic response to the β₁,α₁-adrenergic agonist dobutamine. Male and female PGC-1α^+/+ (<i>n</i> = 6) and PGC-1α^−/− (<i>n</i> = 6) mice at 10–12 wk of age were anesthetized and a 1.4-French Millar catheter was placed through the carotid artery into the left ventricle as described in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0030101#s4" target="_blank">Materials and Methods</a>. Heart rate (left graph) and a measurement of ventricular systolic performance, dP/dt (right graph), were measured following infusion of dobutamine. * <i>p</i> < 0.05.</p>