Gated dynamic 31P MRS shows reduced contractile phosphocreatine breakdown in mice deficient in cytosolic creatine kinase and adenylate kinase
Hermien E. KanAndor VeltienH. ArntsChristine NabuursBart LuijtenA. de HaanBé WieringaArend Heerschap
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Abstract 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.Keywords:
Creatine kinase
Adenosine triphosphate
Adenine nucleotide
Creatine
Energy charge
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Energy charge
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Changes in adenine nucleotides and adenylate energy charge in shake cultures of Penicillium digitatum were determined under conditions when ethylene biosynthesis was either activated or inhibited. Activation of ethylene biosynthesis under phosphate-limiting growth conditions was accompanied by a 28% decrease in the ATP level of the mycelia. Under these growth conditions, changes in the adenylate energy charge were inversely related to the concentration of AMP but did not correlate with changes in the rate of ethylene biosynthesis or in total adenylate nucleotides. Adenine and AMP, when added individually, partially prevented the inhibitory effect of 0.01 mM orthophosphate on ethylene biosynthesis. On addition of orthophosphate, orthophosphate and adenine, or orthophosphate and AMP a rapid decrease within 2 hours in ethylene biosynthesis occurred without a striking increase in the ATP level of the cultures. In non-growing mycelia of P. digitatum, there was considerable modulation in the concentration of individual adenine nucleotides but only small changes in the adenylate energy charge were observed. The data indicated that levels of adenylates, glutamate, or the adenylate energy charge do not mediate or limit phosphate inhibition of ethylene biosynthesis. However, it is suggested that an orthophosphate-repressible phosphatase and/or a protein kinase may be involved in this process.
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Concentration of ATP, total content of adenine nucleotides and energy charge of the adenylate system were distinctly higher in blood of patients with psoriasis as compared with corresponding patterns of healthy persons blood. In psoriasis the rate of glycolytic production of ATP was unaltered in erythrocytes, whereas Na+, K+-ATPase activity was decreased in the cell membranes. Similar alterations occurred in epidermis impaired with psoriasis. The data obtained suggest the systemic type of the pathological process, which caused impairment of adenine nucleotides metabolism. Estimation of ATP concentration, of total content of adenine nucleotides and adenylate energy charge might be of importance in diagnosis and therapy of psoriasis.
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CONTROL OF ENZYME ACTIVITIES 201 Photosynthetic CO2 Fixation 202 Starch Metabolism 204 Glycolysis ..... . . ..... . ........ . ... .. ... . . . . . . . .... . . . . . ...... . . .... ..... . ....... ... . . . . . . . . . . . .... . 204 Tricarboxylic Acid Cycle 205 Other Enzymes 205
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Content of ATP and AMP, total intracellular pool of adenine nucleotides, the ratio of adenylate cyclase affecting ratio of ATP/ADP, energy change of the adenylate system as well as potential of adenine nucleotides phosphorylation were decreased in testicular tissue of rats with alloxan diabetes. At the same time, content of ADP and inorganic phosphate was increased as compared with control values. The data obtained suggest that energy metabolism was distinctly impaired in rat testes under conditions of alloxan diabetes, which appears to occur as a result of decrease in AMP biosynthesis and in transformation of the nucleotide into ATP during oxidative phosphorylation. These alterations in the pool of adenylates appear to play an important role in impairments of spermatogenic and endocrine functions of testes in diabetes.
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