The effects of magnetic field on the biomechanics parameters of soleus and extensor digitorum longus muscles in rats with streptozotocin-induced diabetes

PubMedID: 18715203Background: The aim of this study was to determine the effects of the magnetic field (MF) on the isometric contractile characteristics of the soleus and extensor digitorum longus (EDL) muscles in rats both with and without diabetes. Methods: Biomechanical parameters were recorded in vitro from Wistar rats without diabetes (Group I, n = 20), rats without diabetes exposed to MF (Group II, n = 20), rats with streptozotocin-induced diabetes (Group III, n = 20), and rats with diabetes exposed to MF (Group IV, n = 20). Muscle strips were taken from the distal tendon soleus and EDL muscles of rats killed by decapitation. The muscles were hung in organ baths containing Krebs solution (pH 7.4) with a gas mixture of 95% O2 and 5% CO2. Then the muscles were triggered to direct supramaximal stimulation with 0.05 Hz frequency square pulses for periods of 0.5 ms to obtain control values. The contractile parameters were also determined for two muscles of the four groups. Later, the tension-frequency relationship was determined by applying stimulating pulses of 10, 20, 50, and 100 Hz to the muscles. Results: Diabetes caused a certain amount of decrease in the contractile force of the two muscles compared with that of control values. However, MF increased the contractile force of the two muscles in rats both with and without diabetes. The isometric contraction forces obtained by different stimulating frequencies showed a significant linear increase in the tetanic contraction (P < 0.05). Diabetes increased the contraction time of the isometric twitch tension compared with that of the control group with a statistically significant difference (P < 0.05). MF decreased the contraction time of the two muscles of rats without diabetes (P < 0.05) but increased that of rats with diabetes (P > 0.05). Conclusion: In our study, these results suggest that MF exposure regulates the isometric contractile characteristics of the soleus and EDL muscles of rats with diabetes, positively. © 2008 Mary Ann Liebert, Inc