Expression of Myosin Heavy Chain Isoforms in Rat Soleus Muscle Spindles After 19 Days of Hypergravity

• Published in: The journal of histochemistry and cytochemistry 2003-11, Vol.51 (11), p.1479-1489
• Main Authors: Picquet, Florence, De-Doncker, Laurent, Falempin, Maurice
• Format: Article
• Language: English
• Subjects: Animals; Body Weight; Densitometry; Hypergravity; Immunohistochemistry; Male; Muscle Spindles - metabolism; Muscle, Skeletal - anatomy & histology; Muscle, Skeletal - diagnostic imaging; Muscle, Skeletal - metabolism; Myosin Heavy Chains - biosynthesis; Organ Size; Protein Isoforms - biosynthesis; Rats; Rats, Wistar; Space life sciences; Ultrasonography; Weightlessness
• ISSN: 0022-1554; 1551-5044
• DOI: 10.1177/002215540305101108

The aim of this study was to determine whether a period of 19 days in hypergravity was long enough to induce changes in the expression of myosin heavy chain (MyHC) isoforms in the muscle spindles. The soleus muscle of 10 male Wistar rats (control: CONT, n=5; hypergravity: HG, n=5) was frozen, cut into serial sections, and labeled with antibodies against MyHCs: I, IIA, IIA + IIX + IIB, slow-tonic, and α-cardiac. Forty CONT and 45 HG spindles were analyzed. The results from HG spindles compared to CONT showed that there was no change in the cross-sectional area of intrafusal fibers. However, along the entire length of B1 fibers, the expression of both MyHC I and α-cardiac was increased significantly, whereas the labeling against MyHC IIA and MyHC slow-tonic was decreased. In B2 fibers, the labeling against MyHC IIA (region A), slow-tonic (region A), and fast myosins (regions A-C) was statistically decreased. In chain fibers, the labeling against both MyHC IIA and fast MyHC was reduced significantly. We conclude that hypergravity has a real impact on the MyHC content in the muscle spindles and induces some inverse changes of those observed in hypogravity for MyHCs I, α-cardiac, and slow-tonic.