Glial K(+) Clearance and Cell Swelling: Key Roles for Cotransporters and Pumps

TY - JOUR

T1 - Glial K(+) Clearance and Cell Swelling

T2 - Key Roles for Cotransporters and Pumps

AU - Macaulay, Nanna

AU - Zeuthen, Thomas

PY - 2012/11

Y1 - 2012/11

N2 - An important feature of neuronal signalling is the increased concentration of K(+) in the extracellular space. The K(+) concentration is restored to its original basal level primarily by uptake into nearby glial cells. The molecular mechanisms by which K(+) is transferred from the extracellular space into the glial cell are debated. Although spatial buffer currents may occur, their quantitative contribution to K(+) clearance is uncertain. The concept of spatial buffering of K(+) precludes intracellular K(+) accumulation and is therefore (i) difficult to reconcile with the K(+) accumulation repeatedly observed in glial cells during K(+) clearance and (ii) incompatible with K(+)-dependent glial cell swelling. K(+) uptake into non-voltage clamped cultured glial cells is carried out by the Na(+)/K(+)-ATPase and the Na(+)/K(+)/Cl(-) cotransporter in combination. In brain slices and intact optic nerve, however, only the Na(+)/K(+)-ATPase has been demonstrated to be involved in stimulus-evoked K(+) clearance. The glial cell swelling associated with K(+) clearance is prevented under conditions that block the activity of the Na(+)/K(+)/Cl(-) cotransporter. The Na(+)/K(+)/Cl(-) cotransporter is activated by increased K(+) concentration and cotransports water along with its substrates. It thereby serves as a K(+)-dependent molecular water pump under conditions of increased extracellular K(+) load.

AB - An important feature of neuronal signalling is the increased concentration of K(+) in the extracellular space. The K(+) concentration is restored to its original basal level primarily by uptake into nearby glial cells. The molecular mechanisms by which K(+) is transferred from the extracellular space into the glial cell are debated. Although spatial buffer currents may occur, their quantitative contribution to K(+) clearance is uncertain. The concept of spatial buffering of K(+) precludes intracellular K(+) accumulation and is therefore (i) difficult to reconcile with the K(+) accumulation repeatedly observed in glial cells during K(+) clearance and (ii) incompatible with K(+)-dependent glial cell swelling. K(+) uptake into non-voltage clamped cultured glial cells is carried out by the Na(+)/K(+)-ATPase and the Na(+)/K(+)/Cl(-) cotransporter in combination. In brain slices and intact optic nerve, however, only the Na(+)/K(+)-ATPase has been demonstrated to be involved in stimulus-evoked K(+) clearance. The glial cell swelling associated with K(+) clearance is prevented under conditions that block the activity of the Na(+)/K(+)/Cl(-) cotransporter. The Na(+)/K(+)/Cl(-) cotransporter is activated by increased K(+) concentration and cotransports water along with its substrates. It thereby serves as a K(+)-dependent molecular water pump under conditions of increased extracellular K(+) load.

U2 - 10.1007/s11064-012-0731-3

DO - 10.1007/s11064-012-0731-3

M3 - Review

C2 - 22367475

SN - 0364-3190

VL - 37

SP - 2299

EP - 2309

JO - Neurochemical Research

JF - Neurochemical Research

IS - 11

ER -