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Gated dynamic 31 P MRS shows reduced contractile phosphocreatine breakdown in mice deficient in cytosolic creatine kinase and adenylate kinase
Author(s) -
Kan Hermien E.,
Veltien Andor,
Arnts Henk,
Nabuurs Christine I. H. C.,
Luijten Bart,
de Haan Arnold,
Wieringa Bé,
Heerschap Arend
Publication year - 2009
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.1364
Subject(s) - phosphocreatine , creatine kinase , adenylate kinase , contraction (grammar) , adenosine triphosphate , chemistry , medicine , endocrinology , muscle contraction , adenine nucleotide , creatine , energy charge , biology , biochemistry , energy metabolism , enzyme , nucleotide , gene
We developed a new dedicated measurement protocol for dynamic 31 P MRS analysis in contracting calf muscles of the mouse, using minimally invasive assessment of the contractile force combined with the acquisition of spectroscopic data gated to muscle contraction and determination of phosphocreatine (PCr) recovery rate and ATP contractile cost. This protocol was applied in a comparative study of six wild type (WT) mice and six mice deficient in cytosolic creatine kinase and adenylate kinase isoform 1 (MAK −/− mice) using 70 repeated tetanic contractions at two contractions per minute. Force levels during single contractions, and metabolite levels and tissue pH during resting conditions were similar in muscles of MAK −/− and WT mice. Strikingly, muscle relaxation after contraction was significantly delayed in MAK −/− mice, but during repeated contractions, the decrease in the force was similar in both mouse types. Gated data acquisition showed a negligible PCr breakdown in MAK −/− immediately after contraction, without a concomitant decrease in ATP or tissue pH. This protocol enabled the determination of rapid PCr changes that would otherwise go unnoticed due to intrinsic low signal‐to‐noise ratio (SNR) in mouse skeletal muscles combined with an assessment of the PCr recovery rate. Our results suggest that MAK −/− mice use alternative energy sources to maintain force during repeated contractions when PCr breakdown is reduced. Furthermore, the absence of large increases in adenosine diphosphate (ADP) or differences in force compared to WT mice in our low‐intensity protocol indicate that creatine kinase (CK) and adenylate kinase (AK) are especially important in facilitating energy metabolism during very high energy demands. Copyright © 2009 John Wiley & Sons, Ltd.