AJP - Cell Physiology, Vol 254, Issue 4 C560-C563, Copyright © 1988 by American Physiological Society
Effect of fasting on myocardial substrates in male and female rats
D. A. Arnall, W. K. Palmer, W. C. Miller and L. B. Oscai
Department of Physical Education, University of Illinois at Chicago 60680.
Adult male and female rats were fasted for 1, 2, or 3 days to determine its
effect on circulating and endogenous fuels available to the heart. Liver
glycogen was depleted within the first 24 h of food restriction. Plasma
glucose decreased approximately 2.5 mM in both sexes during the 3 days.
Fasting significantly increased plasma beta-hydroxybutyrate to
approximately the same level in female and male rats. Plasma free fatty
acid (FFA) increased approximately 0.2 mM in both groups during the first
24 h without food and remained elevated over the next 2 days. FFA
concentrations were higher in fed female than in fed male rats and remained
significantly higher in female rats throughout the experimental period.
Myocardial glycogen increased 64% during the first 2 days of fasting in the
male rats and stayed elevated on the third day of fasting. In contrast,
heart glycogen of female rats remained unchanged from an initial value of
3.13 mg/g throughout the 3-day fasting period. Endogenous triglyceride (TG)
of male rats decreased from 2.14 +/- 0.09 to 1.41 +/- 0.21 mumol/g during
the first 24 h without food and remained at that level during the second
and third days. Heart TG in female rats fell progressively from 2.36 +/-
0.19 to 1.02 +/- 0.12 mumol/g during the fasting period. Cardiac FFA were
higher in female than in male animals throughout the entire experiment.
These data indicate that quantitative and qualitative metabolic differences
exist between male and female rats stressed by fasting.(ABSTRACT TRUNCATED
AT 250 WORDS)
