Ubiquitin changes in human biceps muscle following exercise-induced damage.

Changes in ubiquitin levels were characterized in human biceps muscle following high-force eccentric exercise. Volunteers performed damaging eccentric-isokinetic actions of the biceps muscle with the non-dominant arm. Protein extracts of biopsy tissue samples taken two days post-exercise were run on SDS polyacrylamide gels, analyzed densitometrically and revealed a 64% higher level of a protein band at 12 kD. New monoclonal immunoblotting techniques identified the band as free ubiquitin. On these blots, free ubiquitin increased in the exercised sample by 55% over the control, and ubiquitin conjugates of varying molecular weights follow a similar pattern. The changes seen in both free and conjugated ubiquitin suggest that their increases are involved in the response to exercise-induced muscle damage.