| Abstract: | 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. |
