Journal
CIRCULATION RESEARCH
Volume 93, Issue 8, Pages 752-758Publisher
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1161/01.RES.0000096363.85588.9A
Keywords
cardiac myocytes; myosin binding protein-C; sarcomere proteins; cardiac contractility; power output
Funding
- NHLBI NIH HHS [R01-HL57852, P01-HL47053] Funding Source: Medline
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Myosin binding protein-C (MyBP-C) is localized to the thick filaments of striated muscle where it appears to have both structural and regulatory functions. Importantly, mutations in the cardiac MyBP-C gene are associated with familial hypertrophic cardiomyopathy. The purpose of this study was to examine the role that MyBP-C plays in regulating force, power output, and force development rates in cardiac myocytes. Skinned cardiac myocytes from wild-type (WT) and MyBP-C knockout (MyBP-C-/-) mice were attached between a force transducer and position motor. Force, loaded shortening velocities, and rates of force redevelopment were measured during both maximal and half-maximal Ca2+ activations. Isometric force was not different between the two groups with force being 17.0+/-7.2 and 20.5+/-3.1 kN/m(2) in wild-type and MyBP-C-/- myocytes, respectively. Peak normalized power output was significantly increased by 26% in MyBP-C-/- myocytes (0.15+/-0.01 versus 0.19+/-0.03 P/P-o . ML/sec) during maximal Ca2+ activations. Interestingly, peak power output in MyBP-C-/- myocytes was increased to an even greater extent (46%, 0.09+/-0.03 versus 0.14+/-0.02 P/P-o . ML/sec) during half-maximal Ca2+ activations. There was also an effect on the rate constant of force redevelopment (k(tr)) during half-maximal Ca2+ activations, with k(tr) being significantly greater in MyBP-C-/- myocytes (WT=5.8+/-0.9 s(-1) versus MyBP-C-/-=7.7+/-1.7 s(-1)). These results suggest that cMyBP-C is an important regulator of myocardial work capacity whereby MyBP-C acts to limit power output.
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