Effect of age on the development of cardiac hypertrophy produced by aortic constriction in the rat.

To test the hypothesis that the capacity to develop left ventricular (LV) hypertrophy might diminish with advancing age, we examined the hypertrophic response to ascending aortic constriction in 3 groups of adult Fischer 344 rats (9 months, 18 months, and 22 months of age). Aortic constriction was created so that aortic cross-sectional areas would be the same for the 3 groups of rats. Four weeks after imposition of aortic constriction, there was no significant difference in peak LV pressure, peak-to-peak and mean systolic pressure gradients between left ventricle and aorta, cardiac output, LV minute work, or cross-sectional area of the aortic constrictions in the 3 groups. In 9-month-old aortic-constricted rats, LV dry wt (LVDW)/body wt, LVDW/tibial length, and myocyte width increased by 23% (p less than 0.01), 14% (p less than 0.01), and 27% (p less than 0.01), respectively, compared with sham-operated rats. In contrast, in 18-month-old and 22-month-old aortic-constricted rats, LVDW/body wt and LVDW/tibial length were unchanged compared with sham-operated controls, and increases in myocyte width were only modest 4 weeks following constriction. RNA concentration in the myocardium 5 days after constriction increased by 21% (p less than 0.001) in 9-month-old rats but showed no significant rise in 18-month-old rats. These results suggest that advancing age is associated with a diminished capacity to develop myocardial hypertrophy in response to acute pressure overload and that a reduced ability to synthesize protein may be one of the major contributing factors to a diminished capacity for hypertrophy in advanced age.