Figure 2. Transient and reversible effects of H₂O₂ on myofibrillar contractile function .

Original [Ca²⁺]_i and force records from submaximal (50 Hz) contractions of single FDB muscle fibres exposed to H₂O₂ (300 μm) for up to 8 min (A) and H₂O₂ for 6 min followed by exposure to the reducing agent DTT (1 mm) for 10 min (B). Note that H₂O₂ causes major force changes whereas [Ca²⁺]_i is little affected, which means that H₂O₂ mainly acts at the myofibrillar level. The effects on force are time dependent with brief H₂O₂ exposure resulting in increased submaximal force, which is followed by a progressive force decline (A). Furthermore, the force depression caused by prolonged H₂O₂ exposure is reversed by reduction with DTT (B). Conversely, prolonged exposure to DTT results in depressed submaximal force that can be reversed by application of H₂O₂ (not shown). Figure adapted from Andrade et al. (1998).