Saturable transport of Ca into CSF in chronic hypo- and hypercalcemia.
J Neurosci Res
; 30(2): 421-6, 1991 Oct.
Article
in En
| MEDLINE
| ID: mdl-1798059
To further characterize possible saturable transport of Ca into CSF during chronic plasma [Ca] changes, weanling rats were fed diets differing in Ca for 10 weeks. Transfer coefficients for unidirectional uptake of 45Ca and 36Cl into CSF (Kcsf) were determined 3 or 10 min after intravenous tracer injection in unanesthetized animals. In rats fed low Ca diet, Kcsfs for 45Ca and 36Cl were elevated above control, but the 45Ca/36Cl ratio for Kcsf, a more specific measure of Ca transport, was also increased. In animals fed high Ca diet, Kcsfs of both radiotracers were not statistically different from control, but the 45Ca/36Cl ratio was decreased. Injection of CaCl2 into hypocalcemic rats elevated plasma [Ca], depressed 45Ca Kcsf, and returned the 45Ca/36Cl ratio to the control value. The inverse relationship between plasma ionized [Ca] and 45Ca Kcsf was fitted to saturation kinetics with Km less than or equal to 0.53 mumol/ml, maximal Ca influx for the saturable component between 27 and 67 x 10(-5) mumol.g-1.s-1, and the passive component of Kcsf less than or equal to 15 x 10(-5) ml.g-1.s-1. We conclude that Ca transport into CSF is saturable and this transport is important in the regulation of CSF [Ca].
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Calcium
/
Hypercalcemia
/
Hypocalcemia
Limits:
Animals
Language:
En
Journal:
J Neurosci Res
Year:
1991
Document type:
Article