Alterations in cardiac myosin isozymes associated with aging and chronic hypertension: their modulation with nifedipine.
OBJECTIVE
Pressure induced left ventricular hypertrophy is associated with alterations in distribution of cardiac myosin isozymes. This study evaluated the influence of aging, superimposed chronic hypertension on aging, and treatment with nifedipine on cardiac myosin isozyme proportions.


METHODS
Myosin isozyme (V1, V2, and V3) proportions were investigated by pyrophosphate gel electrophoresis, and left ventricular to body weight ratio was studied in two subgroups each of hypertensive and normotensive rats, with and without nifedipine treatment. Nifedipine treatment was started at 48 weeks and concluded at 60 weeks.


RESULTS
For all four groups, the V1 level was the lowest (range 15%-24%), V3 was the highest (47%-60%), and V2 was intermediate (25%-29%). The left ventricular weight to body weight ratio was 25% higher (p < 0.001) in the untreated old hypertensive v old rats, but V1 level was of the same magnitude in both these groups. The left ventricular weight to body weight ratio was 18% lower (p < 0.001) in the old hypertensive treated v untreated rats. The V1 level was higher in both treated groups; old normotensive as well as old hypertensive rats. The changes in V1 were not statistically correlated with arterial pressure and left ventricular to body weight ratio.


CONCLUSIONS
The profound decrease in V1 myosin isozyme proportion acquired with aging is not accentuated by superimposed chronic hypertension. The aging process, and not the left ventricular hypertrophy by itself, seems to be the principal determinant of the myosin isozyme shift. The myosin isozyme shift that occurs with aging is not fixed, and can be partially reversed or prevented by nifedipine.
Raizada
V
V
Department of Medicine, University of New Mexico, Albuquerque 87131.
Pathak
D
D
Blomquist
T M
TM
Minser
R
R
Woodfin
B
B
D000375:Aging / Q000378:metabolism*; D000818:Animals; D002908:Chronic Disease; D004591:Electrophoresis, Polyacrylamide Gel; D006973:Hypertension / Q000188:drug therapy / Q000201:enzymology*; D017379:Hypertrophy, Left Ventricular / Q000201:enzymology; D008297:Male; D009206:Myocardium / Q000201:enzymology*; D009218:Myosins / Q000032:analysis / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D013053:Spectrophotometry
D009218:Myosins; D009543:Nifedipine