Experimental and modelling evidence of shortening heat in cardiac muscle.

摘要: KEY POINTS Heat associated with muscle shortening has been repeatedly demonstrated in skeletal muscle, but its existence cardiac remains contentious after five decades of study. By iterating between experiments and computational modelling, we show compelling evidence for the heat reveal, mechanistically, source this excess heat. Our results clarify a long-standing uncertainty field energetics. We provide revised partitioning energy expenditure to include newly revealed thermal component. ABSTRACT When shortens against an afterload, that it liberates is greater than produced by same contracting isometrically at level force. This defined as 'shortening heat', not muscle. Given micro-structural similarities these two types, since imagine accompaniment cross-bridge cycling, have re-examined issue. Using our flow-through microcalorimeter, measured force generated isolated rat trabeculae undergoing isometric contractions different lengths work-loop (shortening) afterloads. simulated experimental protocols using thermodynamically constrained model cycling probed mechanisms underpinning Predictions were subsequently validated further set experiments. Both modelling convincing Its magnitude inversely related afterload or, equivalently, directly extent shortening. Computational simulations reveal arises from cross-bridges, rate ATP hydrolysis more sensitive change length afterload.