NOS1 and disease of the tendon: Following injury to a tendon, NO is produced by all three isoforms of NOS17: NOS activity is upregulated in tendinopathy.15 In an exercise-overuse model of tendon degeneration, i-NOS, e-NOS and b-NOS mRNAs were overexpressed in the supraspinatus tendon of rats subjected to treadmill running for 14 days40.