title: Cardiac glycosides ouabain and digoxin interfere with the regulation of glutamate transporter GLAST in astrocytes cultured from neonatal rat brain.
abstract: Glutamate transport (GluT) in brain is mediated chiefly by two transporters GLT and GLAST, both driven by ionic gradients generated by (Na(+), K(+))-dependent ATPase (Na(+)/K(+)-ATPase). GLAST is located in astrocytes and its function is regulated by translocations from cytoplasm to plasma membrane in the presence of GluT substrates. The phenomenon is blocked by a naturally occurring toxin rottlerin. We have recently suggested that rottlerin acts by inhibiting Na(+)/K(+)-ATPase. We now report that Na(+)/K(+)-ATPase inhibitors digoxin and ouabain also blocked the redistribution of GLAST in cultured astrocytes, however, neither of the compounds caused detectable inhibition of ATPase activity in cell-free astrocyte homogenates (rottlerin inhibited app. 80% of Pi production from ATP in the astrocyte homogenates, IC50 = 25 μM). Therefore, while we may not have established a direct link between GLAST regulation and Na(+)/K(+)-ATPase activity we have shown that both ouabain and digoxin can interfere with GluT transport and therefore should be considered potentially neurotoxic.
authors.affiliation: Discipline of Anatomy and Histology, School of Medical Sciences, Bosch Institute of Biomedical Research, Sydney Medical School, The University of Sydney, Anderson Stuart Building F 13, Sydney, NSW 2006, Australia.
authors.forename: Khoa T D
authors.initials: KT
authors.lastname: Nguyen
authors.forename: Vlado
authors.initials: V
authors.lastname: Buljan
authors.forename: Paul L
authors.initials: PL
authors.lastname: Else
authors.forename: David V
authors.initials: DV
authors.lastname: Pow
authors.forename: Vladimir J
authors.initials: VJ
authors.lastname: Balcar
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D001921:Brain / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D004077:Digoxin / Q000494:pharmacology*; D027341:Excitatory Amino Acid Transporter 1 / Q000378:metabolism*; D007150:Immunohistochemistry; D010042:Ouabain / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
chemical_list: D027341:Excitatory Amino Acid Transporter 1; C493392:Slc1a3 protein, rat; D010042:Ouabain; D004077:Digoxin; D000254:Sodium-Potassium-Exchanging ATPase