Bone and muscle atrophy with suspension of the rat

Abstract

A modification of the Morey tail suspension model was used to determine atrophic responses of rat bone and muscle with 14-90 days unloading of the hindlimbs. Bone uptake of methylene diphosphonate followed a phasic pattern similar to changes in bone formation rate in immobilized dogs and rats. Increased uptake at 60 days (P = 0.01, femur) indicated an increased bone metabolism. Regional densitometry demonstrated a preferential loss of bone mineral in the trabecular mass (P = 0.02) at 30 days and in the cortical shaft by 90 days (P = 0.03). Maximal muscle atrophy occurred within 14-30 days. The gastrocnemius was less severely affected by suspension than by immobilization techniques, whereas the soleus atrophied (by weight) similarly, suggesting that muscle atrophy in the suspension model is distinctly different from immobilization atrophy. One significant response of skeletal muscle to suspension was an altered blood distribution. Muscle blood distribution changes reflect the hypodynamic state of muscle that continues to contract but probably at an altered rate in response to altered functional demands.

Loss of Bone Strength is Dependent on Skeletal Site in Disuse Osteoporosis in Rats

“…The immobilization-induced loss of rectus femoris muscle mass after 4 weeks was 61% in the present study, which is comparable to a loss of soleus muscle mass of 50% after 30 days of tail suspension observed by LeBlanc et al [50]. The loss of CSA of individual striated muscle cells followed the same overall temporal pattern as muscle mass and muscle CSA.…”

Quantitative assessment of degenerative changes in soleus muscle after hindlimb suspension and recovery

“…Definitions as in Table 1 (Schellock et al 1985). We can hypothesize that maintaining approximately 45°o f suspension, as in the present experiment, enhanced the alterations previously reported in hindlimb muscle blood flow (LeBlanc et al 1985). An additional hypothesis to explain HS-induced muscle damage could be the reduced working length of the SOL muscle, and phasic contractions without load (See Riley et al 1990;Sancesario et al 1992) Whether maintaining HS rats at 45°tilt increased the angle of the ankle joint, and decreased the working range of the SOL muscle remains to be elucidated.…”

Regional blood flow in conscious rats after head-down suspension

“…LeBlanc et al (1985) have suggested a decline in aerobic metabolism after HDS and hence changes in the contractile properties of the soleus muscle ®bre, the muscle continuing to contract but probably at an altered rate in response to the modi®ed functional requirements. McDonald et al (1992b), have also shown that the atrophied soleus muscle was more prone to fatigue, with a corresponding decrease in the release of vasodilatory metabolites (McDonald et al 1992a).…”

“…A reference blood sample was withdrawn via the femoral catheter (0.6 ml á min A1 ), a few seconds prior to microsphere injection and continued for 2 min after microsphere injection. The total infused radioactivity was obtained by comparison with a standard prepared at the time of injection (LeBlanc et al 1985).…”

“…Only the study of Martel et al (1996), has shown hypotension in rats during recovery from hindlimb suspension for 24 h (tachycardia and reduced blood pressure respectively 5±25 min and 25±35 min after recovery). LeBlanc et al (1985) have studied bone and muscle blood¯ows after 14 to 90 days of suspension. Both blood¯ows were reduced after 2 weeks of HDS, and this decrease persisted throughout 90 days of suspension.…”