TY - JOUR
T1 - A "give" in tension and sarcomere dynamics in cardiac muscle relaxation.
AU - Krueger, J. W.
AU - Tsujioka, K.
AU - Okada, T.
AU - Peskin, C. S.
AU - Lacker, H. M.
PY - 1988
Y1 - 1988
N2 - Isometric relaxation in cardiac sarcomeres is characterised by an early, very slow phase of tension fall which is terminated by a 'give' in tension. A 'give' which occurs during relaxation in cardiac muscle can not be attributed to decrease in myofilament overlap. After the 'give' asynchronous motion occurs between sarcomeres, but the duration and extent of their displacement is limited. Intriguingly, the effect of isotonic displacements on the early fall in the velocity of sarcomere shortening indicates that an internal resistance increases near the peak of contraction. The complex shape of the sarcomere's complete force-velocity relation, with lengthening motions in particular, was consistent with an idealized model of cross-bridge cycling. The sarcomere's resistance to stretch is high at low velocity, but it diminishes to reveal yielding at larger velocities. Relative to tension, the resistance to yielding does not decrease during relaxation, and it may actually increase. The decay of isometric tension after a controlled stretch also slows during relaxation. Consequently, cycling slows in those cross-bridges which form (or persist but produce less force) later in contraction. Changes in cross-bridge properties may restrict sarcomere shortening, prolong activation, but promote a disequilibrium which favors rapid relaxation in cardiac muscle.
AB - Isometric relaxation in cardiac sarcomeres is characterised by an early, very slow phase of tension fall which is terminated by a 'give' in tension. A 'give' which occurs during relaxation in cardiac muscle can not be attributed to decrease in myofilament overlap. After the 'give' asynchronous motion occurs between sarcomeres, but the duration and extent of their displacement is limited. Intriguingly, the effect of isotonic displacements on the early fall in the velocity of sarcomere shortening indicates that an internal resistance increases near the peak of contraction. The complex shape of the sarcomere's complete force-velocity relation, with lengthening motions in particular, was consistent with an idealized model of cross-bridge cycling. The sarcomere's resistance to stretch is high at low velocity, but it diminishes to reveal yielding at larger velocities. Relative to tension, the resistance to yielding does not decrease during relaxation, and it may actually increase. The decay of isometric tension after a controlled stretch also slows during relaxation. Consequently, cycling slows in those cross-bridges which form (or persist but produce less force) later in contraction. Changes in cross-bridge properties may restrict sarcomere shortening, prolong activation, but promote a disequilibrium which favors rapid relaxation in cardiac muscle.
UR - http://www.scopus.com/inward/record.url?scp=0023676861&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0023676861&partnerID=8YFLogxK
M3 - Article
C2 - 3407532
AN - SCOPUS:0023676861
SN - 0065-2598
VL - 226
SP - 567
EP - 580
JO - Advances in experimental medicine and biology
JF - Advances in experimental medicine and biology
ER -