AJP - Regulatory, Integrative and Comparative Physiology, Vol 244, Issue 3 407-R411, Copyright © 1983 by American Physiological Society
Metabolic organization of muscle and brown fat of normal and dystrophic hamsters
S. J. Wickler and B. A. Horwitz
The thermogenic response to catecholamines, i.e., regulatory nonshivering
thermogenesis (NST), is significantly reduced in dystrophic hamsters (BIO
14.6) compared with age-matched normals. The possibility that this
reduction reflects, in part, lower levels of enzymes in those tissues
implicated in NST has been examined by assaying citrate synthase (CS),
beta-hydroxyacyl CoA dehydrogenase (HOAD), and phosphofructokinase (PFK),
enzymes whose activity reflect the potential flux of substrates through the
tricarboxylic acid cycle, beta-oxidation, and glycolysis, respectively.
Each enzyme was assayed in brown fat, heart, gastrocnemius, and
semitendinosus of 3-mo-old normal (n = 15) and dystrophic (n = 18)
hamsters. Brown fat masses from interscapular, cervical, and
scapular-axillary regions of dystrophics averaged only 50% those of normals
(424 vs. 890 mg). Additionally, markers of aerobic metabolism (CS and HOAD)
were significantly reduced in the brown fat from dystrophic animals. (CS
activities averaged 59% of normal, whereas HOAD activities averaged 75% of
normal). In dystrophic animals CS and HOAD levels were similar to those of
normals in cardiac tissue but were significantly elevated in skeletal
muscle samples. Tissue PFK activities were reduced only in cardiac tissue
of the more affected dystrophics. Thus decreased NST capacity in dystrophic
hamsters is accompanied by reduced masses and CS values in brown fat but
not by decreases in the aerobic markers in skeletal or cardiac muscle.
