Abstract
In vivo exercise and insulin may change the concentrations of GLUT-4 protein and mRNA in muscle. We studied in vitro whether adaptations in glucose transporter expression are initiated during a single prolonged period of contractions or during insulin stimulation. Rat hindquarters were perfused at 7 mM glucose for 2 h with or without insulin (> 20,000 microU/ml) while the sciatic nerve of one leg was stimulated to produce repeated tetanic contractions. During electrical stimulation, contraction force decreased 93 +/- 1% (SE; n = 26) and muscle glycogen was markedly diminished (P < 0.05). Both contractions and insulin markedly increased glucose transport and uptake (P < 0.05). At the end of contractions, glycogen was higher in the presence of than in the absence of insulin (24 +/- 4 vs. 14 +/- 3 mumol/g for the soleus and 13 +/- 2 vs. 8 +/- 1 mumol/g for the red gastrocnemius, respectively; P < 0.05). In nonstimulated muscle, glucose transporter mRNA and protein concentrations were higher in the soleus than in the white gastrocnemius (GLUT-4 mRNA 184 +/- 18 vs. 131 +/- 36 arbitrary units; GLUT-1 mRNA 173 +/- 29 vs. 114 +/- 26 arbitrary units; GLUT-4 protein 0.96 +/- 0.09 vs. 0.46 +/- 0.03 arbitrary units; GLUT-1 protein 0.41 +/- 0.08 vs. 0.19 +/- 0.05 arbitrary units, respectively; P < 0.05). These concentrations were not changed by contractions or insulin. In conclusion, GLUT-1 and GLUT-4 mRNA and protein levels are higher in slow-twitch oxidative than in fast-twitch glycolytic fibers.(ABSTRACT TRUNCATED AT 250 WORDS)
Originalsprog | Engelsk |
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Tidsskrift | Journal of Applied Physiology |
Vol/bind | 78 |
Udgave nummer | 1 |
Sider (fra-til) | 46-52 |
Antal sider | 7 |
ISSN | 8750-7587 |
Status | Udgivet - jan. 1995 |
Udgivet eksternt | Ja |
Emneord
- Animals
- Blood Glucose
- Glucose Transporter Type 1
- Glucose Transporter Type 4
- Glycogen
- Hindlimb
- Immunoblotting
- In Vitro Techniques
- Insulin
- Male
- Monosaccharide Transport Proteins
- Muscle Contraction
- Muscle Proteins
- Muscle, Skeletal
- Physical Exertion
- RNA, Messenger
- Rats
- Rats, Wistar
- Regional Blood Flow