Effects of changes in dietary fatty acids on isolated skeletal
muscle function in rats.
Ayre, Kerry J., and A. J. Hulbert.
Departments of Biomedical and Biological Sciences, University of
Wollongong, Northfields Ave, Wollongong N.S.W. 2522, AUSTRALIA
APStracts 2:0445A, 1995.
The effects of manipulating dietary levels of essential
polyunsaturated fatty acids on the function of isolated skeletal
muscles in male Wistar rats were examined. Three isoenergetic diets
were used: an essential fatty acid deficient diet, EFAD; a diet high
in essential (n-6) fatty acids, High (n-6); and a diet enriched with
essential (n-3) fatty acids, High (n-3). After nine weeks, groups of
rats on each test diet were fed a stock diet of laboratory chow for a
further six weeks. Muscle function was examined using a battery of
five tests for soleus ("slow" twitch) and extensor digitorum
longus (EDL, "fast" twitch). Tests included single muscle
twitches, sustained tetanic contractions, post-tetanic potentiation,
sustained high frequency stimulation and intermittent low frequency
stimulation. Results for muscles from the High (n-6) and High (n-3)
groups were very similar. However, the EFAD diet resulted in
significantly lower muscular tensions and reduced response times when
compared with the High (n-6) and High (n-3) diets. Peak twitch
tension in soleus muscles was 16-21% less in the EFAD group than the
High (n-6) and High (n-3) groups, respectively (ANOVA, P <
0.01). Also, twitch contraction and half-relaxation times were
significantly 5-7% reduced in the EFAD group (ANOVA, P < 0.01).
During high frequency stimulation, EDL muscles from the EFAD rats
fatigued 32% more quickly (ANOVA, P < 0.01). During intermittent
low frequency stimulation, soleus muscles from the EFAD group
generated 25-28% less tension than the other groups (ANOVA, P <
0.01) but in EDL muscles from the EFAD group, endurance was 20%
greater than in the High (n-6) group (ANOVA, P < 0.05). After
six weeks on the stock diet, there were no longer any differences
between the dietary groups. Manipulation of dietary fatty acids
results in significant, but reversible, effects in muscles of rats
fed an EFAD diet.
Received 20 December 1994; accepted in final form 14 September
1995.
APS Manuscript Number A1291-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95