AJP - Regulatory, Integrative and Comparative Physiology, Vol 258, Issue 1 193-R197, Copyright © 1990 by American Physiological Society
Metabolic effects of aminophylline in weanling rats
M. G. Vonlanthen, R. J. McCarter and D. T. Casto
Department of Pediatrics, University of Texas Health Science Center, San Antonio 78284.
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.
