Myocardial contractility and ventricular myosin isoenzymes as influenced by cardiac hypertrophy and its regression.
Changes in myocardial contractility and ventricular myosin isoenzymes were examined during pressure-overloaded cardiac hypertrophy in rats. Effects of regression of cardiac hypertrophy were also examined. Cardiac hypertrophy was induced by abdominal aortic constriction in 7-week-old male Wistar rats. Regression of cardiac hypertrophy was obtained by opening the aortic band. Myocardial contractility was estimated by measuring isometrically developed tension and maximum rate of tension rise (+dT/dtmax) in isolated left-ventricular papillary muscles perfused with Tyrode solution (32 degrees C, pH 7.4, bubbled with 95% O2.5% CO2, stimulation frequency: 0.2 Hz). Left-ventricular myosin isoenzymes were separated by pyrophosphate gel electrophoresis and the isoenzyme pattern was determined by densitometry. Isometrically developed tension (T) in hypertrophic myocardium remained unchanged, but +/-dT/dtmax decreased as compared with hearts of normal rats. Decreased +/-dT/dtmax recovered near to the level in normal rats by regression of cardiac hypertrophy. Left-ventricular myosin isoenzyme pattern shifted towards VM-3 in hypertrophied myocardium and shifted again toward VM-1 by regression of cardiac hypertrophy. In conclusion, myocardial contractility and ventricular myosin isoenzymes were changed in pressure-overloaded hypertrophy in rats and these changes were reversible to a normal level by regression of cardiac hypertrophy.
Tanamura
A
A
Department of Internal Medicine, Aoto Hospital, Jikei University, School of Medicine, Tokyo, Japan.
Takeda
N
N
Iwai
T
T
Tuchiya
M
M
Arino
T
T
Nagano
M
M
D000818:Animals; D006332:Cardiomegaly / Q000378:metabolism*; D006352:Heart Ventricles; D007527:Isoenzymes / Q000378:metabolism*; D008297:Male; D009200:Myocardial Contraction; D009206:Myocardium / Q000201:enzymology*; D009218:Myosins / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D007527:Isoenzymes; D009218:Myosins