CEREBRAL CALCIUM FLUXES AND CALCIUM HOMEOSTASIS IN THE RAT - A MINIMAL MODEL

Disturbance of calcium homeostasis and unregulated increase in intrace llular calcium have been implicated in cell damage and cell death in t he central nervous system in particular. To determine the specific pat hway(s) of cerebral Ca transport of importance in a pathophysiological situation, we have measured long term Ca flux in brain in vivo in rat , and developed a kinetic model incorporating physiologically relevant pathways of cerebral Ca transport Ca-45 was injected into a rail vein in conscious rats. plasma Ca was monitored up to 4 days post-injectio n and Ca-45 uptake determined in samples of cerebrospinal fluid (CSF) and at several sites of brain at euthanasia. Uptake of the tracer by t issues peaked after 1 h, isotopic equilibration taking longer. The upt ake at hippocampus was the highest. Computer simulation of the kinetic s of the plasma, CSF and tissue data was performed using a compartment al model, which included two subcompartments (intra- and extra-cellula r) and two pathways from plasma to the brain: directly across the bloo d-brain barrier and via CSF, which included a delay. The analysis base d on this model enabled estimation of the fractional rates of transpor t of Ca to cerebral and noncerebral tissues across all the barriers of the model.