Uptake and distribution of 45Ca in the brain of chronically uremic rats.

The exchange of calcium between serum, cerebrum and cerebral mitochondria was studied in chronically uremic rats. Chemical and radiocalcium assays were performed at periods from 1 to 48 h following intracardiac injection of 45Ca. The disappearance of 45Ca from the serum of uremic rats was identical to that observed in normals. Maximal uptake and equilibration with serum by both cerebrum and cerebral mitochondria were assessed in uremic rats by means of relative specific activities (RSAs) and found not to differ significantly from normal. Peak levels occurred at 6 h for cerebrum and between 4 and 6 h for mitochondria. These results indicate that in the rat, calcium uptake by the brain over a period of 48 h is not altered by chronic renal failure. Moreover, the findings in brain mitochondria suggest that the intracellular calcium burden may not be increased by uremia.