Increased mRNAs for procollagens and key regulating enzymes in rat skeletal muscle following downhill running

The purpose of the study was to investigate pre-translational regulation of collagen expression after a single bout of exercise. We analysed steady-st ate messenger ribonucleic acid (mRNA) levels for collagen types I, III and IV, alpha- and beta-subunits of prolyl 4-hydroxylase and lysyl oxidase (enz ymes modifying procollagen chains), and enzyme activity of prolyl il-hydrox ylase from rat soleus muscle (MS) and the red parts of quadriceps femoris m uscle (MQF) after 12 h and after 1, 2, 4, 7 and 14 days of downhill (-13.5 degrees) treadmill running at a speed of 17 m.min(-1) for 130 min. Histolog ical and biochemical assays revealed exercise-induced muscle damage in MQF but not MS. Steady-state mRNA levels for the alpha- and beta-subunits of pr olyl 4-hydroxylase in MQF, lysyl oxidase in MS and MQF were increased 12 h after running, whereas prolyl 4-hydroxylase activity did not increase until 2 days after exercise. The mRNA levels for the fibrillar collagens (I and III) and basement membrane type IV collagen significantly increased 1 day a nd 12 h after exertion, respectively. Peak mRNA levels were observed 2-4 da ys after running, the increases being more pronounced in MQF than in MS. No significant changes were observed in types I or III collagen at the protei n level. Strenuous downhill running thus causes an increase in gene express ion for collagen types I and III and their post-translational modifying enz ymes in skeletal muscle in a co-ordinated manner. These changes, together w ith the increased gene expression of type IV collagen, may represent the re generative response of muscle extracellular matrix to exercise-induced inju ry and an adaptive response to running exertion.