Effects of varying intensity exercise on shortening and intracellular calcium in ventricular myocytes from streptozotocin (STZ)-induced diabetic rats

This study examined the influence of two intensities of exercise on ventricular myocyte shortening and intracellular calcium in the streptozotocin (STZ)-induced diabetic rat. Animals were divided into four groups: control sedentary (CS), diabetic sedentary (DS), diabetic light exercise (DLE; 5 × 30 min/week, 9 m/min) and diabetic moderate exercise (DME; 5 × 30 min/week, 18 m/min) and the exercise programme started 2 months after STZ treatment. Time to peak (TPK) shortening was prolonged in myocytes from DS (112.1 ± 2.5 ms) compared to CS (98.1 ± 2.1 ms) rats and was not additionally altered by either light (117.0 ± 2.1 ms) or moderate (115.4 ± 2.0 ms) exercise. TPK of the Ca²⁺ transient was not significantly altered by STZ treatment (69.4 ± 2.4 ms) but was prolonged by light (79.8 ± 3.5 ms) and moderate (76.6 ± 2.9 ms) exercise compared to CS (65.5 ± 2.7 ms). Data from this study suggest that the chosen intensities of exercise were ineffective in modulating the dynamics of cardiac muscle contraction and reversing the deleterious effects of diabetes on heart-muscle contraction.