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This study was designed to explore the effects of aging and
dietary restriction on the mechanical properties of the
arterial system. Long-Evans male rats fed ad libitum at the age
of 4,6,12 and 18 months were classified into group 1,2,3 and 4,
respective- ly. Food restricted rats with intermittent feeding
were 4 months of age for group 1-d and 18 months of age for
group 4-d. Pulsati- le pressure and flow signals in the
ascending aorta were measured in every anesthetized, opened-
chest rat. Flow phase spectra were corrected by the time-domain
method. These data were subjected to Fourier analysis for
impedance spectra. In the study of aging pr- ocess, we found
that both the static and pulsatile hemodynamics remained
unchanged from development to maturation. Interestingly, the
elderly rats exhibited lower values (p< 0.05) in heart rate,
aortic pressure, peripheral resistance, aortic characteristic
im- pedance and ventricular external power. We speculated that
lumen diameter in the vasculature dilated to cause decrease in
periphe- ral resistance and aortic characteristic impedance in
the elderly rats. In the experiment of dietary restriction, the
food-restric- ted rats showed lower values in body weight as
compared with their age-matched control ones. Decrease in mean
aortic pressure and peripheral resistance were observed in rats
in group 1-d but not in group 4-d. Group 4-d had lower heart
rate and higher stroke volume when normalized to body weight.
Both food-restrict- ed groups exhibited higher values in aortic
compliance as compar- ed with their age-matched controls. In
food-restricted rats of 4 months age, we found a decrease in
aortic blood pressure was the main factor that gave rise to an
increase in aortic compliance. But in food-restricted rats of
18 months age, an increase in aor- tic compliance chiefly came
from an increase in stroke volume.
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