A high-energy focused microwave system for killing experimental animals was used to rapidly inactivate
enzymes and prevent postmortem breakdown of
adenine nucleotides and
adenosine, thereby enabling accurate measurements of
AMP,
ADP,
ATP and
adenosine in rat brain. For comparison,
purine levels were measured in brains of rats killed by
decapitation,
decapitation into liquid
nitrogen, or in situ freezing of the brain with liquid
nitrogen. Of the three microwave irradiation power levels used, 10, 6.0 or 3.5 kW, rats killed by 10 kW had the highest
ATP levels (28.8 nmol/mg
protein) and cellular energy charge value (0.8), and the lowest levels of
AMP (2.2 nmol/mg
protein) and
adenosine (19.7 pmol/mg
protein). Of the 6 brain regions studied,
adenosine levels (pmol/mg
protein) ranged from 10 in cerebral cortex to 170 in cerebellum of rats killed using 10 kW microwave irradiation and, for comparison, ranged from 840 in cerebral cortex to 2498 in striatum of rats killed by
decapitation. Focused microwave killing permits precise and accurate measurements of
purines in discrete regions of rat brain.