title: Microwave irradiation decreases ATP, increases free [Mg²⁺], and alters in vivo intracellular reactions in rat brain.
abstract: Rapid inactivation of metabolism is essential for accurately determining the concentrations of metabolic intermediates in the in vivo state. We compared a broad spectrum of energetic intermediate metabolites and neurotransmitters in brains obtained by microwave irradiation to those obtained by freeze blowing, the most rapid method of extracting and freezing rat brain. The concentrations of many intermediates, cytosolic free NAD(P)(+) /NAD(P)H ratios, as well as neurotransmitters were not affected by the microwave procedure. However, the brain concentrations of ATP were about 30% lower, whereas those of ADP, AMP, and GDP were higher in the microwave-irradiated compared with the freeze-blown brains. In addition, the hydrolysis of approximately 1 μmol/g of ATP, a major in vivo Mg(2+) -binding site, was related to approximately five-fold increase in free [Mg(2+) ] (0.53 ± 0.07 mM in freeze blown vs. 2.91 mM ± 0.48 mM in microwaved brains), as determined from the ratio [citrate]/[isocitrate]. Consequently, many intracellular properties, such as the phosphorylation potential and the ∆G' of ATP hydrolysis were significantly altered in microwaved tissue. The determinations of some glycolytic and TCA cycle metabolites, the phosphorylation potential, and the ∆G' of ATP hydrolysis do not represent the in vivo state when using microwave-fixed brain tissue.
authors.affiliation: Laboratory of Metabolic Control, National Institute on Alcohol Abuse and Alcoholism, NIH, Bethesda, Maryland, USA.
authors.forename: Shireesh
authors.initials: S
authors.lastname: Srivastava
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kashiwaya
authors.forename: Xuesong
authors.initials: X
authors.lastname: Chen
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Geiger
authors.forename: Robert
authors.initials: R
authors.lastname: Pawlosky
authors.forename: Richard L
authors.initials: RL
authors.lastname: Veech
mesh_terms: D000255:Adenosine Triphosphate / Q000032:analysis* / Q000378:metabolism / Q000528:radiation effects; D000818:Animals; D001921:Brain / Q000378:metabolism / Q000528:radiation effects*; D001923:Brain Chemistry / Q000528:radiation effects*; D019075:Electrophoresis, Capillary; D005615:Freezing; D008401:Gas Chromatography-Mass Spectrometry; D042541:Intracellular Space / Q000737:chemistry / Q000528:radiation effects*; D008274:Magnesium / Q000032:analysis*; D008297:Male; D008872:Microwaves; D051381:Rats; D017207:Rats, Sprague-Dawley; D016707:Tissue Fixation / Q000379:methods*
chemical_list: D000255:Adenosine Triphosphate; D008274:Magnesium