Myocardial functional correlates of cardiac myosin light chain 2 phosphorylation.
In vitro and in situ studies have proposed a potentiation of submaximal force production after myosin light chain 2 (P-light chain) phosphorylation in mammalian striated muscle. The purpose of this study was to ascertain the relationship between the augmentation in left ventricular pressure development and cardiac myosin P-light chain phosphorylation at different times during and after submaximal treadmill exercise involving adult female Sprague-Dawley rats. In vivo hemodynamic measurements were monitored with an indwelling high-fidelity solid-state pressure transducer. Exercise heart rate, peak left ventricular (LV) pressure, and rate of LV pressure development/relaxation (LV +/- dP/dt) were significantly elevated compared with a normal sedentary group (P less than 0.001). Peak LV pressure remained significantly elevated throughout 20 min of postexercise recovery (P less than 0.01), and heart rate, LV end-diastolic pressure, and LV +/- dP/dt returned rapidly to preexercise values. Corresponding to these in vivo hemodynamic changes, increased levels of P-light chain phosphorylation were observed during both exercise (16%, P less than 0.01) and subsequent recovery periods (14%, P less than 0.02) compared with the NC group. A quasi-temporal relationship was observed between postexercise peak LV pressure potentiation and P-light chain phosphorylation. These results demonstrate that cardiac myosin P-light chain phosphorylation is associated, in part, with the augmentation of peak LV pressure observed during both exercise and recovery.
Fitzsimons
D P
DP
Department of Physiology and Biophysics, University of California, Irvine 92717.
Bodell
P W
PW
Baldwin
K M
KM
D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D005260:Female; D006321:Heart / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology; D009200:Myocardial Contraction / Q000502:physiology; D009206:Myocardium / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism*; D010766:Phosphorylation; D005082:Physical Exertion / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains
D009218:Myosins