title: Inhibition of chloride outward transport by gadolinium in cultured rat spinal cord neurons.
abstract: Gadolinium is a rare-earth lanthanide metal ion and is used as organic gadolinium complexes in magnetic resonance imaging (MRI). Although gadolinium-based MRI agents are thought to be safe in clinical use, the in vivo release of the toxic free inorganic gadolinium (Gd3+) has been reported in some patients with kidney disease. In central nervous system neurons, the inhibitory action of GABA is a consequence of relatively hyperpolarized Cl- equilibrium potential (ECl), which results from the activity of K+-Cl- co-transporter (KCC). The lanthanide ions are reported to affect GABAA receptors. However, little is known about the effect of Gd3+ on GABAA receptor function with intact intracellular Cl- concentration. In the present study, we investigated the effect of Gd3+ on GABAA receptor-mediated currents using gramicidin perforated patch recording method in cultured rat spinal cord neurons. The application of muscimol, a GABAA receptor agonist, caused outward current at a holding potential of -50 mV. Gd3+ inhibited the muscimol-induced outward current in a concentration-dependent and reversible manner. Gd3+ inhibited the maximum muscimol response but had no effect on the half-maximum concentration. The Gd3+ inhibition was accompanied by a depolarizing shift of the reversal potential. The Gd3+ action was blocked by furosemide, a blocker of both KCC and Na+-K+-Cl- co-transporter (NKCC), but not bumetanide, a specific blocker of NKCC. Gd3+ failed to inhibit the muscimol-induced outward currents recorded by conventional whole-cell patch-clamp method which cannot retain intact intracellular Cl- concentration. These results suggest that Gd3+ inhibits a KCC function and gives rise to increase in intracellular Cl- concentration. The reduction of outward chloride transport could be related to the neurotoxic effects of Gd3+.
authors.affiliation: Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan. isibasi@nips.ac.jp
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Ishibashi
authors.forename: Kenzo
authors.initials: K
authors.lastname: Hirao
authors.forename: Junya
authors.initials: J
authors.lastname: Yamaguchi
authors.forename: Junichi
authors.initials: J
authors.lastname: Nabekura
mesh_terms: D000818:Animals; D002034:Bumetanide / Q000494:pharmacology; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism*; D005260:Female; D005665:Furosemide / Q000494:pharmacology; D058785:GABA-A Receptor Agonists; D005682:Gadolinium / Q000494:pharmacology*; D009118:Muscimol / Q000494:pharmacology; D009474:Neurons / Q000378:metabolism*; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D011963:Receptors, GABA-A / Q000502:physiology; D049994:Sodium Potassium Chloride Symporter Inhibitors; D064506:Solute Carrier Family 12, Member 2; D013116:Spinal Cord / Q000378:metabolism*; D027981:Symporters / Q000037:antagonists & inhibitors; D000096922:K Cl- Cotransporters
chemical_list: D002034:Bumetanide; D002712:Chlorides; D005665:Furosemide; D058785:GABA-A Receptor Agonists; D005682:Gadolinium; D009118:Muscimol; D011963:Receptors, GABA-A; D049994:Sodium Potassium Chloride Symporter Inhibitors; D064506:Solute Carrier Family 12, Member 2; D027981:Symporters; D000096922:K Cl- Cotransporters; C578879:Slc12a2 protein, rat