Cerebral metabolic studies in vivo by 31P NMR.

Publisher Website
Google Scholar
Abstract
31P NMR studies on the brains of living rabbits were carried out at 32 MHz in a spectrometer having a 200-mm clear bore. Paralyzed pump-ventilated animals under N2O analgesia were inserted into the 1.89-T field and signals were focused in the brain by using a 4-cm surface coil. Several conventional physiological variables were monitored together with 31P spectra during induction and reversal of insulin shock and hypoxic hypoxia sufficient to abolish the EEG and during status epilepticus. A reversible decrease in phosphocreatine stores accompanied by an increase in Pi was detected during hypoglycemia and hypoxia. Similar changes were observed in prolonged status epilepticus but were not reversed. ATP levels fell .apprx. 50% in hypoglycemia but only slightly in the other 2 metabolic stresses. Intracellular pH rose in hypoglycemia; in status epilepticus and hypoxia it fell, but only when cardiovascular function was severely impaired. From the measured NMR parameters and the assumptions that creatine kinase was at equilibrium and that the creatine/phosphocreatine pool was constant, it was possible to calculate the relative changes in cytoplasmic ADP levels associated with these metabolic disturbances.