Synthesis and degradation of type IV collagen in rat skeletal muscle during immobilization in shortened and lengthened positions.
OBJECTIVE
Type IV collagen is a major protein in basement membranes surrounding and supporting skeletal muscle cells. In the present study, we tested the hypotheses that immobilization down-regulates synthesis and up-regulates degradation of type IV collagen in skeletal muscle.


METHODS
mRNA level and concentration of type IV collagen as well as mRNA levels and activities of proteins involved in its degradation were analysed from soleus (SOL), gastrocnemius (GAS) and extensor digitorum longus muscles after immobilization in shortened and lengthened positions for 1, 3 and 7 days.


RESULTS
Following immobilization, type IV collagen mRNA level was decreased in SOL and GAS suggesting down-regulated synthesis of this protein. The mRNA level and activity of matrix metalloproteinase-2 (proMMP-2) were increased in all muscles, while the activity of tissue inhibitor of metalloproteinase-2 was decreased in SOL and GAS. These findings reflect an increased capacity for degradation of type IV collagen.


CONCLUSIONS
As a consequence of decreased synthesis/degradation ratio immobilization reduced the concentration of type IV collagen in all muscles. The regulation of type IV collagen through synthesis and/or degradation seems, however, to be muscle specific. Immobilization in lengthened position seems to delay and partly decrease the net degradation of type IV collagen.
Ahtikoski
A M
AM
Department of Biology of Physical Activity, University of Jyväskylä, Finland.
Koskinen
S O A
SO
Virtanen
P
P
Kovanen
V
V
Risteli
J
J
Takala
T E S
TE
D000818:Animals; D015152:Blotting, Northern; D024141:Collagen Type IV / Q000096:biosynthesis / Q000378:metabolism*; D017364:Collagenases / Q000378:metabolism; D004792:Enzyme Precursors / Q000378:metabolism; D018093:Gelatinases / Q000378:metabolism; D007103:Immobilization / Q000502:physiology*; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9; D061965:Matrix Metalloproteinase Inhibitors; D008666:Metalloendopeptidases / Q000378:metabolism; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000378:metabolism*; D009693:Nucleic Acid Hybridization / Q000379:methods; D011480:Protease Inhibitors / Q000378:metabolism; D011489:Protein Denaturation; D012333:RNA, Messenger / Q000032:analysis; D011863:Radioimmunoassay / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000378:metabolism
D024141:Collagen Type IV; D004792:Enzyme Precursors; D061965:Matrix Metalloproteinase Inhibitors; D011480:Protease Inhibitors; D012333:RNA, Messenger; D019716:Tissue Inhibitor of Metalloproteinase-2; D017364:Collagenases; D018093:Gelatinases; D008666:Metalloendopeptidases; C120487:pro-matrix metalloproteinase 9; C069860:progelatinase; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9