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1 Physiology, University of Wisconsin-Madison, Madison, Wisconsin, United States
2 Medicine, University of Wisconsin-Madison, Madison, Wisconsin, United States
* To whom correspondence should be addressed. E-mail: sbrickson{at}physiology.wisc.edu.
Cardiac myosin binding protein-C (cMyBP-C) is a thick filament-associated protein that binds tightly to myosin and has a potential role for modulating myocardial contraction. We tested the hypothesis that cMyBP-C (1) contributes to the enhanced in vivo contractile state following
-adrenergic stimulation and (2) is necessary for myocardial adaptation to chronic increases in afterload. In vivo pressure-volume relations demonstrated that left ventricular (LV) systolic and diastolic function were compromised under basal conditions in cMyBP-C-/- mice compared to wild-type (WT). Moreover, while
-adrenergic treatment significantly improved ejection fraction, peak elastance and the time to peak elastance in WT mice, these functional indices remained unchanged in cMyBP-C-/- mice. Morphological and functional changes were measured through echocardiography in anesthetized mice following five weeks of aortic banding. Adaptation to pressure overload was diminished in cMyBP-C-/- mice as characterized by lack of an increase in posterior wall thickness, increased LV diameter, deterioration of fractional shortening and prolonged isovolumic relaxation time. These results suggest that the absence of cMyBP-C significantly diminishes in vivo LV function and markedly attenuates the increase in LV contractility following
-adrenergic stimulation or adaptation to pressure overload.
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