@entity19 muscles lacking both mitochondrial ( @entity45302 ) and cytoplasmic (MM-CK) @entity908 kinase (CK-/-) show depressed mechanical performance in association with low muscle @entity855 and enhanced @entity15129 content. The aims of the present study were to elucidate the possible role of low @entity855 and high @entity15129 content in impairment of mechanical performance in CK-/- @entity19 and to establish whether CK-/- muscles are able to sustain repeated series of high-intensity contractions. The dorsal flexors of CK-/- and control @entity19 were subjected in situ to two series of 12 tetanic contractions using a custom-made @entity19 isometric dynamometer. The muscle content of high-energy phosphates was analysed by HPLC. @entity855 content declined from 20.6+/-1.9 to 15.5+/-2.4 micromol x g(-1) dry weight (d.w.); @entity15129 content increased from 1.2+/-0.4 to 2.4+/-1.1 micromol x g(-1) d.w. during the first contraction series in CK-/- muscle. Despite these unfavourable changes, maximal torque developed during the first contraction of either series did not differ, indicating that the altered content of @entity855 and @entity15129 does not play a decisive role in impaired mechanical performance in CK-/- @entity19 . The relative decline in torque during the two series did not differ in CK-/- (-20.4+/-6.6 vs. -23.8+/-9.9%). In contrast, wild-type (WT) muscles showed a significantly more pronounced decline during the second series (-12.3+/-7.4 vs. -20.1+/-6.8%). Muscle @entity855 and @entity15129 content did not change in CK-/-, whereas in WT @entity15129 content increased significantly during the second contraction series. These findings indicate that CK-/- tolerate repeated series of high-intensity contractions better than WT, while in CK-/- muscle an additional source of energy is mobilised to regenerate @entity855 during the second series.

XXXX muscles deficient in @entity908 kinase tolerate repeated series of high-intensity contractions.

@entity45302 :: ('12716(Tax:10090)', 'Gene') :: ['Mi-CK'] @entity19 :: ('10090', 'Species') :: ['mice', 'mouse', 'Murine'] @entity908 :: ('MESH:D003401', 'Chemical') :: ['creatine'] @entity15129 :: ('MESH:D007291', 'Chemical') :: ['IMP'] @entity855 :: ('MESH:D000255', 'Chemical') :: ['ATP']
@entity19 :: (10090,Species) :: ['Murine']
