Effects of intravenous anesthetics on the activity of glutamate transporter EAAT3 expressed in Xenopus oocytes: evidence for protein kinase C involvement.
We investigated the effects of the intravenous anesthetics, thiopental, etomidate and ketamine, on the activity of one type of glutamate transporters, EAAT3 (excitatory amino acid transporter type 3). Rat EAAT3 was expressed in Xenopus oocytes by injection of its mRNA. Using two-electrode voltage clamp, membrane currents were recorded after the application of L-glutamate (30 microM) in the presence or absence of various concentrations of the anesthetics. Thiopental (0.3-30 microM) and ketamine (3-1000 microM) did not affect EAAT3 activity. Etomidate decreased EAAT3 activity in a concentration-dependent manner (0.10-10 microM). Etomidate at 1 microM significantly decreased the Vmax, but not the Km of EAAT3 for glutamate. Chelerythrine, a protein kinase C (PKC) inhibitor, significantly decreased EAAT3 activity, however, there were no statistical differences among the chelerythrine, etomidate or chelerythrine plus etomidate groups. Likewise, the combination of staurosporine, another PKC inhibitor, and etomidate did not decrease the responses further compared with staurosporine or etomidate alone. Phorbol-12-myrisate-13-acetate, a PKC activator, abolished etomidate-induced decrease in EAAT3 activity. Since our results showed that thiopental and ketamine did not affect EAAT3 activity significantly, EAAT3 may not be a target for their anesthetic effects. Our results also suggest that etomidate, possibly via PKC, decreased EAAT3 activity at clinically relevant concentrations.
Yun
Jung-Yeon
JY
Department of Anesthesiology and Clinical Research Institute, Seoul National University Hospital College of Medicine, 28 Yongon-Dong, Chongno-Gu, Seoul, 110-744, South Korea.
Kim
Jin-Hee
JH
Kim
Hae-Kyoung
HK
Lim
Young-Jin
YJ
Do
Sang-Hwan
SH
Zuo
Zhiyi
Z
D000470:Alkaloids; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D000818:Animals; D053119:Benzophenanthridines; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005045:Etomidate / Q000494:pharmacology; D050580:Excitatory Amino Acid Transporter 3 / Q000235:genetics / Q000502:physiology*; D005260:Female; D018698:Glutamic Acid / Q000494:pharmacology; D007649:Ketamine / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009865:Oocytes / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D010617:Phenanthridines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D019311:Staurosporine / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013874:Thiopental / Q000494:pharmacology; D014981:Xenopus
D000470:Alkaloids; D018686:Anesthetics, Intravenous; D053119:Benzophenanthridines; D004791:Enzyme Inhibitors; D050580:Excitatory Amino Acid Transporter 3; D010617:Phenanthridines; C493398:Slc1a1 protein, rat; D018698:Glutamic Acid; D007649:Ketamine; C016299:chelerythrine; D011493:Protein Kinase C; D019311:Staurosporine; D013874:Thiopental; D013755:Tetradecanoylphorbol Acetate; D005045:Etomidate