In:
American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, American Physiological Society, Vol. 293, No. 1 ( 2007-07), p. R20-R29
Abstract:
The increase in Ca 2+ sensitivity of isometric force development along with sarcomere length (SL) is considered as the basis of the Frank-Starling law of the heart, possibly involving the regulation of cross-bridge turnover kinetics. Therefore, the Ca 2+ dependencies of isometric force production and of the cross-bridge-sensitive rate constant of force redevelopment ( k tr ) were determined at different SLs (1.9 and 2.3 μm) in isolated human, murine, and porcine permeabilized cardiomyocytes. k tr was also determined in the presence of 10 mM inorganic phosphate (P i ), which interfered with the force-generating cross-bridge transitions. The increases in Ca 2+ sensitivities of force with SL were very similar in human, murine, and porcine cardiomyocytes (ΔpCa 50 : ∼0.11). k tr was higher ( P 〈 0.05) in mice than in humans or pigs at all Ca 2+ concentrations ([Ca 2+ ]) [maximum k tr ( k tr,max ) at a SL of 1.9 μm and pCa 4.75: 1.33 ± 0.11, 7.44 ± 0.15, and 1.02 ± 0.05 s −1 , in humans, mice, and pigs, respectively] but k tr did not depend on SL in any species. Moreover, when the k tr values for each species were expressed relative to their respective maxima, similar Ca 2+ dependencies were obtained. Ten millimolar P i decreased force to ∼60–65% and left ΔpCa 50 unaltered in all three species. P i increased k tr,max by a factor of ∼1.6 in humans and pigs and by a factor of ∼3 in mice, independent of SL. In conclusion, species differences exert a major influence on k tr , but SL does not appear to modulate the cross-bridge turnover rates in human, murine, and porcine hearts.
Type of Medium:
Online Resource
ISSN:
0363-6119
,
1522-1490
DOI:
10.1152/ajpregu.00537.2006
Language:
English
Publisher:
American Physiological Society
Publication Date:
2007
detail.hit.zdb_id:
1477297-8
SSG:
12
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