Abstract
To examine whether a single cardiomyocyte preparation retains the mechanical characteristics of ventricle, we measured the contractile function of a single rat ventricular myocyte under a wide range of loading conditions using a force-length measurement system implemented with adaptive control methods. A pair of carbon fiber was used to clamp the myocyte. One fiber was stiff, serving as a mechanical ground, while the bending motion of the other compliant fiber was monitored for force-length measurement. Furthermore, by controlling the position of the compliant fiber using a piezo-electric translator based on adaptive control strategy, we could change both preload and afterload dynamically during contractions. Under isometric condition, peak developed force reached 41.6±2.7 mN/mm2 (mean±S.E.M., n=17), and under unloaded condition, maximal shortening velocity was 106±5.3 μm/s (n=13). When we simulated physiological loading conditions consisting of an isometric contraction followed by shortening and relaxation, the average work-output was quite close to that expected from the total external work of the left ventricle. The upper left corners of force-length loops obtained under these conditions distributed along a straight line, analogous to the end-systolic pressure-volume relation of the ventricle. [Jpn J Physiol 54 Suppl:S103 (2004)]
