ABSENCE OF MYOFIBRILLAR CREATINE-KINASE AND DIAPHRAGM ISOMETRIC FUNCTION DURING REPETITIVE ACTIVATION

Citation
Jj. Labella et al., ABSENCE OF MYOFIBRILLAR CREATINE-KINASE AND DIAPHRAGM ISOMETRIC FUNCTION DURING REPETITIVE ACTIVATION, Journal of applied physiology, 84(4), 1998, pp. 1166-1173
Citations number
31
Categorie Soggetti
Physiology,"Sport Sciences
ISSN journal
87507587
Volume
84
Issue
4
Year of publication
1998
Pages
1166 - 1173
Database
ISI
SICI code
8750-7587(1998)84:4<1166:AOMCAD>2.0.ZU;2-3
Abstract
Creatine kinase (CK) provides ATP buffering in skeletal muscle and is expressed as 1) cytosolic myofibrillar CK (M-CK) and 2) sarcomeric mit ochondrial CK(ScCKmit) isoforms that differ in their subcellular local ization. We compared the isometric contractile and fatigue properties of I)control CK-sufficient (Ctl), 2) M-CK-deficient (M-CK[-/-]), and 3 ) combined M-CK/ScCKmit-deficient null mutant (CK[-/-]) diaphragm (Dia l to determine the effect of the absence of M-CK activity on Dia perfo rmance in vitro. Baseline contractile properties were comparable acros s groups except for specific force, which was similar to 16% lower in CK[-/-] Dia compared with M-CK[-/-] and Ctl Dia. During repetitive act ivation (40 Hz, 1/3 duty cycle), force declined in all three groups. T his decline was significantly greater in CK[-/-] Dia compared with Ctl and M-CK[-/-] Dia. The pattern of force decline did not differ betwee n M-CK[-/-] and Ctl Dia. We conclude that Dia isometric muscle functio n is not absolutely dependent on the presence of M-CK, whereas the com plete absence of CK acutely impairs isometric force generation during repetitive activation.