Fluoxetine Inhibits K+ Transport Pathways (K+ Efflux, Na+-K+-2Cl− Cotransport, and Na+ Pump) Underlying Volume Regulation in Corneal Endothelial Cells

Fluoxetine Inhibits K+ Transport Pathways (K+ Efflux, Na+-K+-2Cl− Cotransport, and Na+ Pump)... 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 μm by 26%, and 50 μm totally. Fluoxetine had a triphasic effect on K+ efflux; from 20 to 100 μm 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 μm by 25%, and 50 μm completely. Bumetanide (1 μm) inhibited RVI by 43%. In a Cl−-free medium, fluoxetine (50–500 μm) progressively inhibited bumetanide-insensitive K+ influx. The inhibitions of RVI and K+ influx induced by fluoxetine 20 to 50 μm were similar to those induced by 1 μm 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 μm inhibits NKCC, and at 100–1000 μm 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. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Fluoxetine Inhibits K+ Transport Pathways (K+ Efflux, Na+-K+-2Cl− Cotransport, and Na+ Pump) Underlying Volume Regulation in Corneal Endothelial Cells

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Copyright © Inc. by 1999 Springer-Verlag New York
Life Sciences; Biochemistry, general; Human Physiology
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