title: Serotonin-induced calcium signaling via 5-HT1A receptors in human leukemia (K 562) cells.
abstract: In this study, serotonin (5-HT) was found to diminish the intracellular calcium, [Ca2+]i, concentrations in a dose-dependent manner in Fura-2-loaded human leukemia (K 562) cells. Prior addition of verapamil (a calcium channel blocker) to the cells abolished the serotonin-induced response, suggesting that the diminution of free [Ca2+]i contents was due to the opening of calcium channels. Thapsigargin (an agent which increases [Ca2+]i via its action on endoplasmic reticulum) augmented the [Ca2+]i contents. Addition of serotonin before or after thapsigargin (THAP) curtailed the THAP-stimulated increases in [Ca2+]i, supporting the notion that 5-HT acts on the calcium channels and that it empties, in part, the THAP-stimulated calcium contents. Spiperone and NAN-190, antagonists to 5-HT1A receptor subtype, abolished the serotonin effects on calcium signaling, whereas an agonist to 5-HT1A receptor, 8OHDPAT, mimicked the serotonin-like action on the diminution of the intracellular calcium contents. These results indicate that the 5-HT response is mediated via 5-HT1A serotonergic receptors in these cells. Furthermore, we characterized the 5-HT receptors in K 562 cells. The specific binding of serotonin to these cells was saturable and hyperbolic. The Kd and the Bmax of serotonin binding were 100 nM and 1690 fmol/10(6) cells, respectively. 8-[3H]OH-DPAT also labeled these cells with a Bmax of 2.8 fmol/10(6) cells and a Kd of 20 nM. The specific binding of 8-[3H]OH-DPAT to K 562 cells was displaced by serotonin, 8OH-DPAT, and NAN-190. These results suggest that K 562 cells possess functional 5-HT1A receptors coupled with calcium signaling.
authors.affiliation: Laboratoire de Physiologie Animale, Unité d'Immuno-physiologie Générale et Comparée, Limoges, France.
authors.forename: N A
authors.initials: NA
authors.lastname: Khan
authors.forename: F
authors.initials: F
authors.lastname: Ferriere
authors.forename: P
authors.initials: P
authors.lastname: Deschaux
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D006801:Humans; D010879:Piperazines / Q000494:pharmacology; D011985:Receptors, Serotonin / Q000096:biosynthesis* / Q000187:drug effects*; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D014407:Tumor Cells, Cultured / Q000378:metabolism
chemical_list: D010879:Piperazines; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; C058895:1-(2-methoxyphenyl)-4-(4-(2-phthalimido)butyl)piperazine; D012701:Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D002118:Calcium