The effects of preimmobilization training and immobilization on collagen synthesis in rat skeletal muscle.

The activities of prolyl 4-hydroxylase (PH) and galactosylhydroxylysyl glucosyltransferase (GGT), both enzymes of collagen biosynthesis, and the concentration of hydroxyproline (Hyp) were measured in soleus and tibialis anterior muscle after periods of 0, 7 and 21 days of immobilization following a swimming training for a period of three weeks in rats. After swimming, the specific activities of PH and GGT were increased by 25% (N.S.) and 53% (p less than 0.01), respectively, in the soleus muscle. In the tibialis anterior muscle PH was increased by 31% (p less than 0.01) after exercise. During the first week of immobilization, PH activity in the shortened soleus muscle was decreased by 21% (p less than 0.001) and by 65% (p less than 0.001) below the control level in the trained and non-trained groups, respectively. The difference between these two groups is significant (p less than 0.001). The specific activity of PH decreased to control level after one week of immobilization in the tibialis anterior muscle. Hyp concentration increased significantly (p less than 0.05) in the shortened soleus muscle after one week of immobilization due to rapid atrophy of non-collagenous proteins, whereas in the tibialis anterior muscle no significant increase was observed until after three weeks of immobilization. The results suggest that swimming, which contains only concentric muscle work and lacks eccentric and weight bearing components, is a positive regulator of collagen biosynthesis. The results suggest also that preimmobilization training may slow down the deadaptive changes caused by disuse during the first week of immobilization.