Caiozzo VJ, Haddad F, Baker MJ, Herrick RE, Baldwin KM.

ASGSB Bull. 1993 Oct; 7: 79.

Depts. of Physiology and Biophysics and Orthopaedics. University of California, Irvine 92717.

In a companion study, we found that a six day spaceflight mission produced significant increases in the maximal shortening velocity (Vmax) of slow antigravity skeletal muscle. Given the relationship between (Vmax) and myosin heavy chain (MHC) isoforms, the primary objective of this study was to examine alterations in MHC isoform expression at both the protein and mRNA levels. Soleus muscles were obtained from male Sprague-Dawley rats, flown aboard STS-54, 3-8 hrs after landing. The MHC protein and mRNA isoforms of the flight muscles were compared to those of control muscles. MHC protein isoforms were separated by electrophoresis. MHC mRNA isoform analyses were performed by Northern blot hybridization, using oligonucleotides probes that were specific to the 3' untranslated region. The slow Type I and fast Type IIA MHC protein isoforms represented 73 and 27%, respectively, of the total myosin pool in the control soleus muscles. In contrast, the MHC protein pool of the flight muscles was composed of 69% Type 1, 21% Type IIA, and 10% Type IIX MHC isoforms. The relative content of Type I MHC mRNA isoform was unchanged. The relative content of Type IIA and Type IIX MHC mRNA isoforms in the flight muscles were 7 and 230 percent of the control values, respectively. A substantial amount of Type IIB MHC mRNA isoform was also observed in the flight muscles, but not in control muscles. The findings of this study support the general hypothesis that spaceflight increases the fast myosin content of slow skeletal muscle. They further demonstrate that, at both the protein and mRNA levels, these changes occur rapidly. The small changes in Type IIA and Type IIX MHC protein isoforms and the large changes in the corresponding mRNA isoforms might reflect a temporal disparity between transcription and translation. However, this issue can only be resolved by longer space flight missions.

Publication Types:

• Meeting Abstracts

Keywords:

• Animals
• Male
• Muscle, Skeletal
• Muscles
• Myosin Heavy Chains
• Myosins
• Proteins
• RNA, Messenger
• Rats, Sprague-Dawley
• Space Flight
• NASA Discipline Musculoskeletal
• NASA Discipline Number 00-00
• NASA Program Flight
• Non-NASA Center

Other ID:

• 95607960

UI: 102212778

From Meeting Abstracts