AJP - Regulatory, Integrative and Comparative Physiology, Vol 254, Issue 4 648-R654, Copyright © 1988 by American Physiological Society
Effects of exercise, detraining, starvation, and refeeding on lipogenic capacity of Osborne-Mendel rat
P. Lowney, V. M. Lee, R. J. Hansen and J. S. Stern
Department of Nutrition, School of Veterinary Medicine, University of California, Davis 95616.
Both starvation and refeeding and exercise and detraining are procedures
that result in lowered lipid stores followed by their refilling. Rats
subjected to these procedures were evaluated for their ability to produce
hepatic biosynthetic reducing equivalents. Five-week-old male
Osborne-Mendel rats were exercised on a motorized treadmill for 6 wk (final
speed 27 m/min, 60 min/day, 6 day/wk) or kept sedentary. Exercised and
sedentary rats were starved for 48 h or fed ad libitum. After treatments,
some rats in each group were killed. Remaining exercised animals were
detrained or detrained and refed. Remaining sedentary rats were refed.
Activities of hepatic glucose-6-phosphate dehydrogenase, 6-phosphogluconate
dehydrogenase, and malic enzyme were evaluated. Plasma glucose,
triglyceride, insulin, liver triglyceride, and body composition were
determined. Results indicate that changes in lipids stores associated with
starvation and refeeding and exercise and detraining are not associated
with similar changes in enzyme activity. Starvation resulted in lowered
plasma glucose, triglyceride, and insulin. Starvation and all exercise
treatments resulted in lowered carcass fat. Exercised rats who were starved
for 48 h and then detrained and refed for 72 h had the greatest liver
weights and percent liver triglycerides. This was not associated with
similar changes in enzyme activity. Increased liver lipid and decreased
carcass fat may indicate a redistribution of lipid stores in these animals.
