ABSTRACT
In this study metabolic consequences of muscular dystrophy were investigated using the mdx mouse model. Measurements were performed on C57BL/10SNJ (control) and dystrophic (mdx) mice of ages 4-6 weeks (young) and 1 year (adult), i.e. at times when muscle degeneration and regeneration are known to be high (young) and low (adult). Whole body metabolic rate (MR) was measured indirectly under usual living conditions by recording O2 consumption and CO2 production over 24 h. Physical activity of mice was measured simultaneously. Oxygen consumption of soleus (SOL) and extensor digitorum longus (EDL) muscles of control and mdx mice was recorded in vitro, using polarographic O2 electrodes. MR in young mdx was significantly decreased compared to young control, but no differences were found in adults. Also, food consumption and physical activity of mdx were decreased significantly compared to control in young but not in adult mice. There was no difference in resting oxygen consumption of muscles from young mdx and control mice, but oxygen consumption of EDL from adult mdx was less than control. Results suggest that muscular dystrophy results in decreased rate of energy metabolism mainly as a consequence of decreased physical activity. The extensive muscular degeneration and regeneration characteristic of muscular dystrophy therefore do not appear to lead to an increase in whole body metabolism.
Subject(s)
Muscular Dystrophy, Animal/metabolism , Aging/metabolism , Animals , Body Weight/physiology , Eating/physiology , Energy Metabolism/physiology , Female , Male , Mice , Mice, Inbred C57BL , Mice, Neurologic Mutants , Muscles/metabolism , Oxygen Consumption/physiologyABSTRACT
Methylxanthines are commonly used to treat asthma and apnea in infants and children. A physiological effect of these compounds is an elevation of the metabolic rate, but the mechanism of this increase is unclear. We have investigated the hypothesis that this elevation of metabolic rate in young animals is in part due to increased physical activity. Metabolic rate and spontaneous physical activity of weanling Fischer 344 rats were measured before and during 2 days of aminophylline administration. Our results show increased metabolic rate measured over 23 h, concomitant with increased activity during treatment. Resting metabolic rate was not elevated. The results suggest that increased physical activity plays a major role in increasing metabolic rate during aminophylline treatment. Metabolic rate returned to control levels on the 2nd day of treatment despite a smaller but still significant elevation in physical activity. This suggests development of tolerance to the effects of aminophylline on activity together with adaptation to the metabolic effects of this drug.
Subject(s)
Aminophylline/pharmacology , Metabolism/drug effects , Motor Activity/physiology , Animals , Circadian Rhythm , Drinking/drug effects , Male , Motor Activity/drug effects , Rats , Rats, Inbred F344 , Rest , WeaningABSTRACT
Whole body metabolic rate is elevated after administration of methylxanthines, but the mechanism by which this occurs is not clear. We have investigated the hypothesis that this increase in metabolic rate is in part due to increased physical activity. Metabolic rate and spontaneous cage activity of Fischer 344 rats were measured over a 24-h period before and during aminophylline treatment. Weight, food, and water consumption were also measured. Our results show an increase in metabolic rate with a simultaneous increase in spontaneous activity over the 24-h period. These results are consistent with the hypothesis that increased physical activity is in part responsible for the increase in cellular metabolism that follows administration of aminophylline.
