title: Fluoxetine inhibits K(+) transport pathways (K(+) efflux, Na(+)-K(+)-2Cl(-) cotransport, and Na(+) pump) underlying volume regulation in corneal endothelial cells.
abstract: We have studied regulatory volume responses of cultured bovine corneal endothelial cells (CBCEC) using light scattering. We assessed the contributions of fluoxetine (Prozac) and bumetanide-sensitive membrane ion transport pathways to such responses by determining K(+) efflux and influx. Cells swollen by a 20% hypo-osmotic solution underwent a regulatory volume decrease (RVD) response, which after 6 min restored relative cell volume by 98%. Fluoxetine inhibited RVD recovery; 20 microM by 26%, and 50 microM totally. Fluoxetine had a triphasic effect on K(+) efflux; from 20 to 100 microM it inhibited efflux 2-fold, whereas at higher concentrations the efflux first increased to 1.5-fold above the control value, and then decreased again. Cells shrunk by a 20% hyperosmotic solution underwent a regulatory volume increase (RVI) which also after 6 min restored the cell volume by 99%. Fluoxetine inhibited RVI; 20 microM by 25%, and 50 microM completely. Bumetanide (1 microM) inhibited RVI by 43%. In a Cl(-)-free medium, fluoxetine (50-500 microM) progressively inhibited bumetanide-insensitive K(+) influx. The inhibitions of RVI and K(+) influx induced by fluoxetine 20 to 50 microM were similar to those induced by 1 microM bumetanide and by Cl(-)-free medium. A computer simulation suggests that fluoxetine can interact with the selectivity filter of K(+) channels. The data suggest that CBCEC can mediate RVD and RVI in part through increases in K(+) efflux and Na-K-2Cl cotransport (NKCC) activity. Interestingly, the data also suggest that fluoxetine at 20 to 50 microM inhibits NKCC, and at 100-1000 microM inhibits the Na(+) pump. One possible explanation for these findings is that fluoxetine could interact with K(+)-selective sites in K(+) channels, the NKC cotransporter and the Na(+) pump.
authors.affiliation: Department of Ophthalmology, College of Physicians & Surgeons, Columbia University, New York, NY 10032, USA.
authors.forename: E
authors.initials: E
authors.lastname: Hara
authors.forename: P S
authors.initials: PS
authors.lastname: Reinach
authors.forename: Q
authors.initials: Q
authors.lastname: Wen
authors.forename: P
authors.initials: P
authors.lastname: Iserovich
authors.forename: J
authors.initials: J
authors.lastname: Fischbarg
mesh_terms: D000818:Animals; D002034:Bumetanide / Q000494:pharmacology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors*; D002417:Cattle; D048429:Cell Size / Q000187:drug effects; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism; D004728:Endothelium, Corneal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D005473:Fluoxetine / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D017136:Ion Transport / Q000187:drug effects; D007700:Kinetics; D008958:Models, Molecular; D008968:Molecular Conformation; D009997:Osmotic Pressure; D011188:Potassium / Q000378:metabolism*; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000737:chemistry / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D028021:Sodium-Potassium-Chloride Symporters; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*
chemical_list: D002352:Carrier Proteins; D002712:Chlorides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D028021:Sodium-Potassium-Chloride Symporters; D005473:Fluoxetine; D002034:Bumetanide; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium