Vol. 87, Issue 5, 1909-1913, November 1999
Biphasic changes in heart performance with food restriction in
rats
Kelly A.
McKnight,
Heinz
Rupp,
Ken S.
Dhalla,
Robert E.
Beamish, and
Naranjan S.
Dhalla
Institute of Cardiovascular Sciences, St. Boniface General
Hospital Research Centre, and Department of Physiology, Faculty of
Medicine, University of Manitoba, Winnipeg, Manitoba, Canada R2H
2A6
To examine
effects of food restriction resembling very-low-calorie dieting on
heart performance, normal rats were fed 25% of ad libitum food intake
for 14 days. Although heart weight decreased (P < 0.05) after 5 days, left
ventricular systolic pressure as well as rates of pressure development
and fall were increased (P < 0.05)
at 7 days and decreased (P < 0.05)
after 14 days. Systolic and diastolic blood pressures were also
increased from 5 to 7 days and decreased after 14 days. The increased
hemodynamic performance of heart was associated with a raised plasma
norepinephrine concentration, which peaked at day
7 of food restriction; epinephrine concentration was
increased (P < 0.05) also at
day 7. An increased catecholamine synthesis was indicated by the raised
(P < 0.05) plasma dopamine 
-hydroxylase activity at 3 days, but this was decreased
(P < 0.05) at 14 days. The
concentration of dopamine in the heart was increased
(P < 0.05) at 2-14 days, of
norepinephrine at 7-14 days, and of epinephrine at 10 and 14 days.
Food restriction thus appears initially to be associated with an
enhanced catecholamine influence on the heart and is followed by a
depressed cardiac performance.
cardiovascular function; low-calorie dieting; sympathetic activity; plasma catecholamines; cardiac catecholamine stores
