Growth hormone and mild exercise in combination increases markedly muscle mass and tetanic tension in old rats

Abstract

Objective: A decline of skeletal muscle mass and strength is seen with aging and immobilization. Growth hormone (GH) has been shown to increase muscle mass. In the present study the effects of a combination of mild exercise and GH on skeletal musculature tetanic tension, dry defatted weight (DDW), volume, water, fat and collagen concentrations were investigated in old rats. Design: Recombinant human GH (2.7 mg/kg per day) was injected subcutaneously for 73 days in 21-month-old female rats. Exercised rats ran on a treadmill, 8 m/min for 1 h/day. The in vivo maximal tetanic tension of the calf musculature (m. soleus, m. plantaris, m. gastrocnemius together) was analysed in anaesthetized rats by stimulating the ischiadic nerve. Results: The maximal tetanic tension was increased by 23% in GH-injected compared to saline-injected rats. Mild exercise GH in combination resulted in a further 18% increase in maximal tetanic tension. The mild exercise by itself did not in¯uence the maximal tetanic tension signi®cantly when compared with saline injected rats. The GH administration and/or mild exercise did not change skeletal muscle endurance, measured as tetanic tension during 30 s of stimulation. Serum IGF-I concentration was increased twofold in GH-injected rats. Conclusion: The increased muscle mass induced by GH mild exercise was associated with a corresponding increase in maximal tetanic tension. Combination of GH mild exercise resulted in a substantial further increase of muscle mass and maximal tension compared with GH injections alone in these old rats.

Relative effects of exercise training and alendronate treatment on skeletal muscle function of ovariectomized rats

“…23<25 It has also been reported that relatively mild endurance exercise has a synergistic effect on the action of growth hormone on soleus and extensor digitorum longus muscle mass. 26 In the present study ovariectomy may have eliminated the depressive effect that estrogen has on growth hormone or insulin-like growth factor 1 levels. The anabolic effects of these hormones may have then been augmented by the exercise training program, leading to greater hypertrophy than typically observed in endurance training studies using male or intact female rats.…”

Effects of Physical Exercise on Autophagy and Apoptosis in Aged Brain: Human and Animal Studies

“…Furthermore, experiments done in 21-month-old rats showed that mild physical exercise in treadmill (8 m/min, 1 h/day) in combination with GH administration for 73 days, increased both muscle mass and strength compared with GH by itself (110). However, Marzetti et al showed that short-term treadmill training attenuates age-related skeletal muscle apoptosis and the same effect was not observed with short-term administration of GH in older rats (111).…”

Sarcopenia and Age-Related Endocrine Function

“…The effects of GH administration on muscle mass, strength and physical performance are still under debate [19]. In animal models, GH treatment is very effective at inhibiting sarcopenic symptoms such as muscle atrophy and decreases in protein synthesis particularly in combination with exercise training [88]. The effect of GH treatment for elderly subjects is controversial.…”