Creatine kinase (CK) has been implicated in the maintenance of skeletal muscle intracellular energy supply via its ATP buffering capacity. The localization of CK at the mitochondria (CK-mi) and myofibril (CK-M) is postulated to increase the efficiency of energy transduction allowing increased muscle performance. We compared the in vitro (37°) force-velocity properties of the diaphragm (DIA) from I) transgenic mice deficient in both CK-M and CK-mi (double null mutant) and 2} wild type controls (CTL) to characterize the role of CK. Optimal muscle length (Lo: 7.8±0.4 mm) and peak force at L0 (Po: 22±1 N/cm2) were not different between CTL and double null mutant DIA. Maximum velocity of shortening was lower in CKM/CK-mi deficient DIA (Vmax: 14±2 Lo/s) vs. CTL DIA (Vmax: 17±2 Lo/s) ; peak power output was obtained at 0.4 Po in both groups. The ability of CK-M/CK-mi deficient DIA to sustain shortening during repetitive isotonic contractions (75 Hz, 330 me duration repeated each sec at 0.4 Po load) was markedly impaired. CK-M/CK-mi deficient DIA velocity of shortening and power declined to zero by 27±4 sec, whereas CTL DIA power was sustained at 65% of baseline. We conclude that combined CK-M/CK-mi deficiency in DIA profoundly alters shortening capacity during repetitive ieotonic activation, underscoring the functional importance of CK in skeletal muscle.
|Original language||English (US)|
|State||Published - Dec 1 1996|
ASJC Scopus subject areas
- Molecular Biology