The effect of fluoxetine on Ca2+ signaling in Madin-Darby canine kidney (MDCK) cells was investigated by using fura-2 as a Ca2+ probe. Fluoxetine increased [Ca2+]i concentration-dependently between 5 microM and 200 microM with an EC50 value of 40 microM. The response was reduced by external Ca2+ removal by 30%40%. In Ca2+-free medium pretreatment with 1 microM thapsigargin, an inhibitor of the endoplasmic reticulum Ca2+ pump, abolished 100 microM fluoxetine-induced Ca2+ release. Addition of 3 mM Ca2+ to Ca2+-free medium increased [Ca2+]i when cells were pretreated with 100 microM fluoxetine. Suppression of 1,4,5-trisphosphate (IP3) formation by 2 microM U73122 (a phospholipase C inhibitor) did not affect 100 microM fluoxetine-induced Ca2+ release. Fluoxetine (5-100 microM) also increased [Ca2+]i in neutrophils, prostate cancer cells and bladder cancer cells from human and rat glioma cells.

The effect of celecoxib on renal tubular cells is largely unexplored. In Madin Darby canine kidney (MDCK) cells, the effect of celecoxib on intracellular CaCa2+ concentration ([Ca2+]i) and proliferation was examined by using the Ca(2 +)-sensitive fluorescent dye fura-2 and the viability detecting fluorescent dye tetrazolium, respectively. Celecoxib (> or =1 micro M) caused an increase of [CaCa2+]i in a concentration-dependent manner. Celecoxib-induced [CaCa2+]i increase was partly reduced by removal of extracellular CaCa2+. Celecoxib-induced CaCa2+ influx was independently suggested by MnCa2+ influx-induced fura-2 fluorescence quench. In Ca(2 +)-free medium, thapsigargin, an inhibitor of the endoplasmic reticulum Ca(2 +)-ATPase, caused a monophasic [CaCa2+]i increase, after which celecoxib only induced a tiny [CaCa2+]i increase; conversely, pretreatment with celecoxib completely inhibited thapsigargin-induced [CaCa2+]i increases. U73122, an inhibitor of phospholipase C, abolished ATP (but not celecoxib)-induced [CaCa2+]i increases. Overnight incubation with 1 or 10 micro M celecoxib decreased cell viability by 80% and 100%, respectively. These data indicate that celecoxib evokes a [CaCa2+]i increase in renal tubular cells by stimulating both extracellular CaCa2+ influx and intracellular CaCa2+ release and is highly toxic to renal tubular cells in vitro.