Effect of denervation on adenine nucleotides in skeletal muscle from normal and dystrophic mice

Liquid chromatography method for simultaneous quantification of ATP and its degradation products compatible with both UV-Vis and mass spectrometry

ATP and its degradation products are essential metabolic and signaling molecules. Traditionally, they have been quantified via high-performance liquid chromatography (HPLC) with UV-Vis detection while utilizing phosphate buffer mobile phase, but this approach is incompatible with modern mass detection. The goal of this study was to develop an ultra-performance liquid chromatography (UPLC) method free of phosphate buffer, to allow for analysis of adenine nucleotides with UV-Vis and mass spectrometry (MS) simultaneously. The final conditions used an Acquity HSS T3 premier column with a volatile ammonium acetate buffer to successfully separate and quantify ATP-related analytes in a standard mixture and in extracts from non-contracted and contracted mouse hindlimb muscles. Baseline resolution was achieved with all 10 metabolites, and a lower limit of quantification down to 1 pmol per inject was observed for most metabolites using UV-Vis. Therefore, this method allows for the reliable quantification of adenine nucleotides and their degradation products via UV-Vis and their confirmation and/or identification of unknown peaks via MS.

Low energy charge in human uterine muscle

Six pregnant and 10 non-pregnant patients undergoing Caesarean section and laparatomy, respectively participated in this study which was aimed at determining the energy status of human uterine muscle and comparing it to that of striated muscle from the same individual. Biopsies were taken from the fundus uteri between the ligamenta rotunda and from the rectus abdominis muscle. A low energy charge of 0.55 in pregnant patients and 0.64 in non-pregnant patients was observed in uterine biopsies, compared to the expected value of 0.90 found in rectus biopsies. The main determinant of this finding was a 4-8 times lower level of ATP in uterine biopsies compared to that in rectus biopsies. The same pattern was apparent for total nucleotide content and creatine phosphate. The ADP and AMP contents were of the same order of magnitude in both tissues. The lactate content in uterine biopsies from pregnant patients was significantly higher than that found in biopsies from rectus muscle and from uterine tissue of non-pregnant patients, indicating an increased glycogenolysis in pregnant uterus. The low energy charge and low level of phospho-compounds observed in uterine muscle, regardless of the functional state, are new and unexpected findings.