Journal of Applied Physiology, Vol 50, Issue 3 482-486, Copyright © 1981 by American Physiological Society
Influence of streptozotocin-induced diabetes and insulin on the functional capacity of rats
R. D. Murphy, A. C. Vailas, C. M. Tipton, R. D. Matthes and J. G. Edwards
Male Sprague-Dawley rats were assigned to three groups designated as
diabetic, diabetic-plus-insulin, and control and tested for maximum oxygen
consumption (VO2max) and maximum heart rate on three different occasions
during the 6- to 8-wk experimental period. Compared with the prediabetic
values and the means of the other two groups, diabetic animals had
significantly higher submaximum and lower maximum VO2 values. These
relationships prevailed when the groups were evaluated in terms of
ml.kg-1.min-1 or ml.(kg0.79-1).min-1. In addition, the diabetic animals had
significantly lower submaximum and maximum heart rates and shorter run
times. Daily injections of insulin (2 U.day-1.rat-1) restored VO2max to
within the limits of the control animals but did not normalize heart rates
or run-time values. The linear relationship between heart rates and VO2 was
repeatedly demonstrated with normal animals. However, this relationship
progressively declined with the time course of diabetes. These results
indicate that, in untreated diabetes, functional capacity is markedly
reduced with the progression of the disease and suggest that alterations in
the autonomic nervous system, tissue metabolic capacity, and decreases in
lean body mass are responsible for the changes noted.
