AJP - Regulatory, Integrative and Comparative Physiology, Vol 269, Issue 2 453-R462, Copyright © 1995 by American Physiological Society
Determination of local rates of 45Ca influx into rat brain by quantitative autoradiography: studies of aging
G. A. Dienel, B. Tofel-Grehl, C. C. Cruz, K. Luludis, K. Pettigrew, L. Sokoloff and G. E. Gibson
Laboratory of Cerebral Metabolism, National Institute of Mental Health, Bethesda, Maryland 20892, USA.
Calcium homeostasis in brain is altered in many conditions, but there is no
method to assay quantitatively local calcium flux into brain in vivo. 45Ca
uptake into gross-dissected brain regions was measured and compared with
results obtained with a quantitative autoradiographic procedure developed
to assay influx of 45Ca into brain. Regional calcium contents,
brain-to-plasma distribution ratios for calcium and 45Ca, apparent
plasma-to-brain transfer coefficients, and net uptake of 45Ca into
gross-dissected regions varied by as much as 80%. Local rates of net uptake
of 45Ca into 34 structures determined by autoradiography varied by 12- to
14-fold, and rates of movement of 45Ca down concentrations gradients varied
by a factor of 7. Previous studies with gross-dissected brain regions
suggested changes in calcium uptake into brain during aging, but the values
of all the variables assayed in the present study were similar in young
adult, middle-aged, and old male rats. A quantitative autoradiographic
procedure to assay levels of 45Ca in brain provides the anatomical
resolution required to investigate local calcium flux in a variety of
physiological and pathological conditions.
