The metabolism of purine and pyrimidine nucleotides in rat cortex during insulin-induced hypoglycemia and recovery.

Brains of paralysed rats with insulin-induced hypoglycemia were frozen in situ after spontaneous EEG activity had been absent for 5 or 15 min ("coma"). Recovery (30 min) was achieved in a different group of rats by administering glucose after a 30-min coma period. Purine and pyrimidine nucleotides, nucleosides and free bases were determined in the cortical extracts by high pressure liquid chromatography (HPLC). The ATP values obtained with the HPLC method were in excellent agreement with those obtained using standard enzymatic/fluorometric techniques, while values for ADP and AMP obtained with the HPLC method were significantly lower. Comatose animals showed a severe (40-80%) reduction in the concentrations of all nucleoside triphosphates (ATP, GTP, UTP and CTP) and a simultaneous increase in the concentrations of all nucleoside di- and monophosphates, including that of IMP. The adenine nucleotide pool size decreased to 50% of control level. The concentrations of the nucleosides adenosine, inosine, and uridine increased 50- to 250-fold, while the concentrations of the purine bases, xanthine and hypoxanthine, rose 2- and 30-fold, respectively. There were no increases in the concentrations of adenine, guanine, or xanthosine. Following glucose administration there was a partial (ATP, UTP and CTP) or almost complete (GTP) recovery of the nucleoside triphosphate levels. During recovery, the levels of nucleoside di- and monophosphates and of adenosine decreased to values close to control; the rise in the inosine level was only partially reversed, and the concentrations of hypoxanthine and xanthine rose further. The adenine nucleotide pool size was only partially restored (to 67% of control value). The adenine nucleotide pool size was not increased by i.p. injection of adenosine or adenine under control condition, or during the posthypoglycemic recovery period.