Metabolic effects of hydrocortisone in mouse brain.

The effect of intramuscular administration of hydrocortisone (10 mg/day per animal) for 5 days has been studied on the content of the amino acids belonging to the glutamate family, in the different regions of the mouse brain, along with the activities of glutamine synthetase, glutamate dehydrogenase, and aspartate, alanine, tyrosine, and ornithine aminotransferases. Further, since proline too is related to glutamate metabolism, the activity of proline oxidase was also studied in these regions. As hydrocortisone is known to influence the ionic fluxes in different tissues and the nitrogen metabolism, the activities of Na(+),K(+)-ATPase together with the content of RNA and protein have also been estimated. A fall in the amino acids of the glutamate family in all three regions was observed with an increase in glutamate dehydrogenase activity in cerebral cortex. A significant fall in the protein content was also observed, mainly in the brain stem. A universal increase in Na(+),K(+)-ATPase activity was observed in all three regions, with the highest in the cerebral cortex. The results indicate that hydrocortisone triggers increased utilization of glutamate in brain as an alternative to glucose, thereby shifting the nitrogen metabolism toward catabolism. The increased activity of Na(+),K(+)-ATPase under these conditions would further aggravate the same and may lead to membrane stabilization.