Mechanoenergetic Estimation of Multiple Cross-Bridge Steps per ATP in a Beating Heart

DOI Web Site PubMed 参考文献42件

この論文をさがす

抄録

The efficiency from the ventricular O2 consumption (VO2) to the total mechanical energy (TME) generated by ventricular contraction has proved relatively constant at ∼35%, independent of the loading and contractile conditions in a canine heart. TME is the sum of the external mechanical work for ejecting a stroke volume against the afterload and of the mechanical potential energy for developing ventricular pressure in each beat. The ∼35% VO2-to-TME efficiency indicates an also constant ∼60% ATP-to-TME efficiency in a beating heart, based on the nominal ∼60% VO2-to-ATP efficiency in the myocardial oxidative phosphorylation. I newly attempted to explain the load-independent ∼60% ATP-to-TME efficiency by the recently reported ∼7–10 nm unitary step size and ∼0.8–1.5 pN unitary force of a cross-bridge (CB) at the molecular level in in vitro motility assays. This single CB behavior suggests that its unitary cycle could generate a mechanical energy of ∼0.6–1.5×10−20 J at most. From the nominal free energy of ∼10×10−20 J per ATP, the efficiency from one ATP to the CB unitary cycle would then be ∼6–15%. This low efficiency is only ∼1/10–1/4 of the ∼60% ATP-to-TME efficiency at the heart level. This discrepancy suggests that each CB would repeat the unitary cycle at least ∼4–10 times per ATP to achieve the high constant ATP-to-TME efficiency in a beating heart. This seems to represent a considerable mechanoenergetic advantage of the heart at the integrative heart level as compared to the molecular CB level.<br>

収録刊行物

参考文献 (42)*注記

もっと見る

キーワード

詳細情報 詳細情報について

問題の指摘

ページトップへ