Antifatigue Effects Of Changbai Mountain Radix Astragali On Skeletal Muscle And Its Mechanisms Of Action

[Objective] To evaluate the antifatigue effects of Changbai Mountain Radix Astragali (CMRA) extracts (aqueous extract, 85% ethanol extract, 50% ethanol extract, n-butanol extract, and ethyl acetate extract) on skeletal muscle and investigate their dose-effect relationship. To study the biochemical and molecular mechanisms of action for the extract possesing strongest activity by the method of biochemical and RT-PCR.[Method] Five kinds of CMRA extracts (aqueous extract, 85% ethanol extract, 50% ethanol extract, n-butanol extract, and ethyl acetate extract) were prepared according to the traditional Chinese herbal extraction procedure. Kunming mouse (male, weight 20-22g) and Wistar rat (male, weight 180-200g) were adopted to the tests. Mice were used to determine the swimming time, the superoxide dismutase (SOD) activity, and the content of malondialdehyde (MDA). Wistar rats were used to measure the skeletal muscle myotility, the superoxide dismutase (SOD) activity and the content of malondialdehyde (MDA) of the skeletal muscle, and the expression ofα-actin of the skeletal muscle in rat was also measured.[Results] 1. Effects of CMRA extracts on loading swimming time and weight of mice: All five kinds of extracts showed the prolonged loading swimming time in different extent. 2. Effects of CMRA aqueous extract on skeletal muscle myotility: (1) A significant enhancement of Pt for the single contraction of the gastrocnemius muscle and soleus muscle was found for the middle dose group and large dose group of the aqueous extract, but the incubation period and half relaxation time for the gastrocnemius muscle were prolonged, while a decurtated incubation period and half relaxation time were found for the single contraction of the soleus muscle; (2) An increased tetanus Pt and a decreased fatigue index (FI) of the the gastrocnemius muscle and soleus muscle were found for the aqueous extract. 3. Effects of CMRA 85% ethanol extract on the skeletal muscle myotility: (1) A prolongation of the decurtated incubation period and half relaxation time of the single contraction, and an increased Pt for the gastrocnemius muscle were found in the large dose group. A decurtated incubation period and half relaxation time, and an increased Pt for the soleus muscle were foud in the middle and large dose groups of the 85% ethanol extract. (2) An increased tetanus Pt and a decreased fatigue index (FI) of the the gastrocnemius muscle and soleus muscle were found for the 85% ethanol extract. 4. Effects of CMRA aqueous extract on the contents of SOD and MDA in the blood serum of mice and the skeletal muscle of rats: (1) An increased activity of SOD in the blood serum of mouse and a significant decrease of the MDA content were found in the middle and large groups of the aqueous extrat. (2) An obvious enhancement of SOD activity and a dignificant decrease of the MDA content were found in the gastrocnemius muscle and soleus muscle in rats. 5. Effects of CMRA 85% ethanol extract on the contents of SOD and MDA in blood serum of mice and skeletal muscle of rats: (1) Only the large dose group of 85% ethanol extract enhanced the SOD activity, while the other dosage groups showed no significant differences and the changes of the contents showed no significant. (2) The changes of the content of SOD and MDA in rat skeletal muscle also showed no significant. 6. Effects of CMRA aqueous extract on theα-actin 's expression_ in rat skeletal muscle: The middle dose and large dose groups showed a significant enhancement for theα-actin expression_ in rat skeletal muscle after intragastric administration of CMRA aqueous extract compaired with control group.[Conclusion] (1) Aqueous extract, 85% ethanol extract, 50% ethanol extract, n-butanol extract and ethyl acetate extract of CMRA showed antifatigue activities to a certen exent and a dose depended propertis, among which the aqueous extrat showed the most significant activity. (2) CMRA could raise the skeletal muscle's contractibility. (3) CMRA increase the activity of SOD, and inhibit the lipid peroxidation in blood and skeletal muscle tissue. (4) CMRA enhance the expression_ ofα-actin mRNA in rat skeletal muscle. (5) It is possible that CMRA exhibit its antifatigue activity via free radical inhibiting effect in blood and skeletal muscle and via enhancing the expression ofα-actin mRNA in skeletal muscle.