Abstract
Abstract The influence of work-induced hypertrophy on the myosin of skeletal muscle was studied. Unilateral tenotomy of the gastrocnemius muscle (single tenotomy procedure) in normal rats led to rapid compensatory growth of the synergistic plantaris and soleus muscles. Total myosin increased with hypertrophy. The myosin from these hypertrophied muscles, however, was enzymatically and structurally identical to the myosin from the contralateral limb muscles. Tenotomy of the plantaris in addition to the gastrocnemius (double tenotomy procedure) caused more rapid hypertrophy of the soleus than that observed with the single tenotomy procedure. The specific activity of the myosin ATPase from these hypertrophied soleus muscles was 11% lower (p l 0.05) than that of the myosin from the controls. However, the alkali stability of the ATPase activity and the light chain content of the myosin from the control and hypertrophied soleus muscles were identical. Thus, only the specific activity of the myosin ATPase accumulated in the soleus muscle during work-induced growth appears to depend on the rate of muscle hypertrophy. Preliminary studies on adult soleus, plantaris, and newborn rat muscle myosin showed that the decrease in specific activity of the hypertrophied soleus myosin ATPase cannot be explained by the selective accumulation of fast muscle or fetal muscle myosin.
Highlights
Compensatory hypertrophy of the soleus and plantaris muscles was induced by tenotomy of the synergist gastrocnemius muscle in 250 to 300 g Sprague-Dawley rats under chloral hydrate (35 mg per kg intraperitoneal) anesthesia
A sham operation was performed on the contralateral limb; the tenotomy and sham operations were alternated between the right and left leg in successive hypertrophy experiments
These authors found a significant decrease of the specific activity of myosin ATPase of hypertrophied rat soleus muscles following the double tenotomy procedure and suggested that a fetal-type of myosin might accumulate in muscles during the early stages of hypertrophy
Summary
Compensatory hypertrophy of the soleus and plantaris muscles was induced by tenotomy of the synergist gastrocnemius muscle (single tenotomy procedure) in 250 to 300 g Sprague-Dawley rats under chloral hydrate (35 mg per kg intraperitoneal) anesthesia. The plantaris tendon was severed (double tenotomy procedure) to increase the extent and rate of hypertrophy of the soleus muscle [2]. All steps were carried out at 4”, and all solutions were made I rnnf with respect to EDTA, and TESi buffer (Sigma), pH 7.0.2 The minced muscle was homogenized five times for 30 s each at low speed (4.6) on a Polytron Homogenizer (Brinkmann) in 10 ml of 0.05 M KCl. The homogenate was centrifuged for 10 min at 1000 g, and the precipitate washed three times with the same solution. The sediment was collected at 6000 x g for 10 min and the supernatant fraction was decanted; the sediment was made 0.5 M with respect to KC1 (by addition of a volume of 1 M KC1 equal to the wet weight of the sediment) and
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