title: Response of infant and adult rat choroid plexus potassium transporters to increased extracellular potassium.
abstract: The choroid plexus (CP) has an important role in regulating ion concentrations in the cerebrospinal fluid (CSF). Maintenance of potassium concentration [( K]) in brain extracellular fluids lower than in serum is critical to proper neuronal function. We studied K (86Rb) transport by the isolated, lateral CP from infant and mature rats to determine the nature and development of CSF [K] regulation. Comparison of transport characteristics in media with 3-11 mM [K] showed that the adult CP increased uptake in a stepwise fashion with each 2 mM increase in [K], up to a 90% increase with 9 mM [K] over control (3 mM [K]). In contrast, 3-day CP increased uptake in 5 mM, but could not increase K uptake further with higher [K]. One-week tissues showed an intermediate response. Kinetic analysis of the ouabain-inhibitable component suggested that the immature tissues may express a different isoform of the catalytic (alpha) subunit of the Na,K-ATPase. These data may explain the previously established inability of neonatal rats to regulate CSF [K] when serum [K] is elevated, and they indicate that active K transport by the CP cells plays an integral role in CSF [K] regulation.
authors.affiliation: Dept. of Clinical Neurosciences, Brown University/Rhode Island Hospital, Providence 02903.
authors.forename: J T
authors.initials: JT
authors.lastname: Parmelee
authors.forename: D
authors.initials: D
authors.lastname: Bairamian
authors.forename: C E
authors.initials: CE
authors.lastname: Johanson
mesh_terms: D000375:Aging; D000818:Animals; D000831:Animals, Newborn; D002831:Choroid Plexus / Q000254:growth & development* / Q000378:metabolism; D007700:Kinetics; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012413:Rubidium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium; D011188:Potassium