Uptake and concentrations of calcium in rat choroid plexus during chronic hypo- and hypercalcemia.
The choroid plexus has been implicated in the regulation of cerebrospinal fluid (CSF) [Ca], but little information is available concerning Ca transport by this epithelium. We determined the transfer coefficients for 45Ca uptake into choroid plexus from blood, as well as tissue [Ca], in weanling Fischer-344 rats fed low, normal, or high Ca diets for 8 weeks. Plasma [Ca] decreased by 45% with low Ca diet and increased by 25% with high Ca diet. Choroid plexus 45Ca uptake varied inversely with plasma [Ca]. This relation was due largely to changes in extracellular Ca binding rather than to entry from blood, as the transfer coefficient was independent of plasma [Ca]. The extracellular Ca distribution in choroid plexus, the intercept of a plot of tissue 45Ca distribution against time, was reciprocally related to plasma [Ca]. Changes in total cell [Ca] during hypercalcemia were equivalent to those in plasma, and in hypocalcemia were 70% of those in plasma. These findings indicate that regulation of CSF [Ca] does not involve saturable transport of Ca into the choroid epithelium from blood, and that the apical membrane of the choroid epithelium is involved in homeostasis of CSF [Ca].
Murphy
V A
VA
Laboratory of Neurosciences, National Institute on Aging, Bethesda, MD 20892.
Smith
Q R
QR
Rapoport
S I
SI
D000818:Animals; D002118:Calcium / Q000493:pharmacokinetics*; D002831:Choroid Plexus / Q000378:metabolism* / Q000503:physiopathology; D006934:Hypercalcemia / Q000378:metabolism*; D006996:Hypocalcemia / Q000378:metabolism*; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344
D002118:Calcium