The Effects Of Hibernation And Hindlimb-unloading On The Blood And The Skeletal Muscle Function Of Ground Squirrel(Spermophilus Dauricus)

Objectives:To study the changes of blood, skeletal muscle function and organ indicators of the ground squirrel (Spermophilus dauricus) during hibernation and under the condition of the hindlimb-unloading. Methods:(1).Divide ground squirrels into 4 groups:pre-hibernation (Pre-H), hibernation (H), post-hibernation (Post-H) and hindlimb-unloading (HU); the hindlimb-unloading model was constructed by tail suspension of the ground squirrel for 14-day according to the tail-suspension model of rat, and it's control group is the Pre-H group. (2).Use the automatic analyzers to detect the serum biochemical indicators and the blood picture. (3). Collect and analyze the data of skeletal muscle funcion through the Powerlab system; the UV spectrophotometer was used to detect the Ca2+-ATPase's activity according to the Pi content. (4). Calculate the organ index and organ water content by their wet weight and dry weight. Results:(1). During the hibernation, the content of total cholesterol (TC) in the serum has increased significantly (+54.38%, p<0.05); the number of platelet has decreased sharply (-69.58%, p<0.05); the peak twitch tension (Pt) and peak tetanic tension (P0) of both soleus(SOL) and extensor digitorum longus(EDL) have decreased significantly; the time to 50% peak tension (TP50), time to peak tension (TPT), time from peak tension to 50% relaxation (RT50) and time from peak tension to 75% relaxation (RT75) have incerased notably; the Ca2+-ATPase's activity of the SOL and EDL has no significant changes during the hibernation. (2). During the period of post-hibernation (Post-H), the concentration of Ca2+has decreased 22.49%(p<0.05); the liver index increased sharply; there was no changes about other indicators during the Post-H. (3). After 14-day-hindlimb unloading, the concentration of total protein and albumin in the serum has droped significantly; no changes was found about the Pt, P0,TP5o, TPT, RT50, RT75 and Ca2+-ATPase's activity of both SOL and EDL; the liver index has sharply increased. Conclusions:(1). The ground squirrel represented a hypercholesterolemia during the hibernation and the high content of cholesterol could be responsible for the energy supply during the long time of torpor. (2) The platelet in the ground squirrel's serum dropped during the hibernation, which would be a countermeasure to prevent the increase of the blood viscosity. (3). Since the Ca2+-ATPase's activity of both SOL and EDL kept stability, the decreas of the muscle tension and the increase of the time course of SOL and EDL of the ground squirrel may be due to the transition of the muscle fiber type:from the fast twitch fiber to the slow twitch fiber.(5). The 14-day-hindlimb-unloading can not induce a significant disuse atrophy in the ground squirrel.