title: Rate of tension redevelopment is not modulated by sarcomere length in permeabilized human, murine, and porcine cardiomyocytes.
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 mum) 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 (DeltapCa(50): approximately 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 mum 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 approximately 60-65% and left DeltapCa(50) unaltered in all three species. P(i) increased k(tr,max) by a factor of approximately 1.6 in humans and pigs and by a factor of approximately 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.
authors.affiliation: Division of Clinical Physiology, Institute of Cardiology, University of Debrecen, Medical and Health Science Center, Faculty of Medicine, H-4004 Debrecen, Hungary.
authors.forename: István Ferenc
authors.initials: IF
authors.lastname: Edes
authors.forename: Dániel
authors.initials: D
authors.lastname: Czuriga
authors.forename: Gábor
authors.initials: G
authors.lastname: Csányi
authors.forename: Stefan
authors.initials: S
authors.lastname: Chlopicki
authors.forename: Fabio A
authors.initials: FA
authors.lastname: Recchia
authors.forename: Attila
authors.initials: A
authors.lastname: Borbély
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Galajda
authors.forename: István
authors.initials: I
authors.lastname: Edes
authors.forename: Jolanda
authors.initials: J
authors.lastname: van der Velden
authors.forename: Ger J M
authors.initials: GJ
authors.lastname: Stienen
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Papp
mesh_terms: D000328:Adult; D000818:Animals; D002118:Calcium / Q000502:physiology; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007537:Isometric Contraction; D008297:Male; D051379:Mice; D008875:Middle Aged; D009200:Myocardial Contraction / Q000502:physiology*; D032383:Myocytes, Cardiac / Q000502:physiology* / Q000648:ultrastructure; D009210:Myofibrils / Q000502:physiology / Q000648:ultrastructure; D012518:Sarcomeres / Q000502:physiology* / Q000648:ultrastructure; D013552:Swine
chemical_list: D002118:Calcium