Myocardial contraction is 5-fold more economical in ventricular than in atrial human tissue.
OBJECTIVE
Cardiac energetics and performance depend on the expression level of the fast (alpha-) and slow (beta-) myosin heavy chain (MHC) isoform. In ventricular tissue, the beta-MHC isoform predominates, whereas in atrial tissue a variable mixture of alpha- and beta-MHC is found. In several cardiac diseases, the slow isoform is upregulated; however, the functional implications of this transition in human myocardium are largely unknown. The aim of this study was to determine the relation between contractile properties and MHC isoform composition in healthy human myocardium using the diversity in atrial tissue.


METHODS
Isometric force production and ATP consumption were measured in chemically skinned atrial trabeculae and ventricular muscle strips, and rate of force redevelopment was studied using single cardiomyocytes. MHC isoform composition was determined by one-dimensional SDS-gel electrophoresis.


RESULTS
Force development in ventricular tissue was about 5-fold more economical, but nine times slower, than in atrial tissue. Significant linear correlations were found between MHC isoform composition, ATP consumption and rate of force redevelopment.


CONCLUSIONS
These results clearly indicate that even a minor shift in MHC isoform expression has considerable impact on cardiac performance in human tissue.
Narolska
N A
NA
Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, van der Boechorststraat 7, 1081BT Amsterdam, The Netherlands. na.narolska@vumc.nl
van Loon
R B
RB
Boontje
N M
NM
Zaremba
R
R
Penas
S Eiras
SE
Russell
J
J
Spiegelenberg
S R
SR
Huybregts
M A J M
MA
Visser
F C
FC
de Jong
J W
JW
van der Velden
J
J
Stienen
G J M
GJ
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016275:Atrial Function / Q000502:physiology*; D001696:Biomechanical Phenomena; D004591:Electrophoresis, Polyacrylamide Gel; D006325:Heart Atria; D006352:Heart Ventricles; D006801:Humans; D008875:Middle Aged; D009200:Myocardial Contraction / Q000502:physiology; D009206:Myocardium / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000378:metabolism; D020033:Protein Isoforms / Q000378:metabolism; D016276:Ventricular Function / Q000502:physiology*
D020033:Protein Isoforms; D000255:Adenosine Triphosphate; D018995:Myosin Heavy Chains