title: Cell density-dependent changes in intracellular Ca2+ mobilization via the P2Y2 receptor in rat bone marrow stromal cells.
abstract: Bone marrow stromal cells (BMSCs) are an interesting subject of research because they have characteristics of mesenchymal stem cells. We investigated intracellular Ca(2+) signaling in rat BMSCs. Agonists for purinergic receptors increased intracellular Ca(2+) levels ([Ca(2+)](i)). The order of potency followed ATP = UTP > ADP = UDP. ATP-induced rise in [Ca(2+)](i) was suppressed by U73122 and suramin, but not by pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), suggesting the functional expression of G protein-coupled P2Y(2) receptors. RT-PCR and immunohistochemical studies also showed the expression of P2Y(2) receptors. [Ca(2+)](i) response to UTP changed with cell density. The UTP-induced rise in [Ca(2+)](i) was greatest at high density. V(max) (maximum Ca(2+) response) and EC(50) (agonist concentration that evokes 50% of V(max)) suggest that the amount and property of P2Y(2) receptors were changed by cell density. Note that UTP induced Ca(2+) oscillation at only medium cell density. Pharmacological studies indicated that UTP-induced Ca(2+) oscillation required Ca(2+) influx by store-operated Ca(2+) entry. Carbenoxolone, a gap junction blocker, enhanced Ca(2+) oscillation. Immunohistochemical and quantitative real-time PCR studies revealed that proliferating cell nuclear antigen (PCNA)-positive cells declined but the mRNA expression level of the P2Y(2) receptor increased as cell density increased. Co-application of fetal calf serum with UTP induced Ca(2+) oscillation at high cell density. These results suggest that the different patterns observed for [Ca(2+)](i) mobilization with respect to cell density may be associated with cell cycle progression.
authors.affiliation: Department of Physiology 2, Kansai Medical University, Osaka, Japan. ichikawj@takii.kmu.ac.jp
authors.forename: Jun
authors.initials: J
authors.lastname: Ichikawa
authors.forename: Hisae
authors.initials: H
authors.lastname: Gemba
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D002229:Carbenoxolone / Q000378:metabolism; D002452:Cell Count; D006801:Humans; D008297:Male; D058910:Purinergic P2 Receptor Agonists; D051381:Rats; D011916:Rats, Inbred F344; D018048:Receptors, Purinergic P2 / Q000235:genetics / Q000378:metabolism*; D058473:Receptors, Purinergic P2Y2; D017154:Stromal Cells / Q000166:cytology / Q000502:physiology*; D014544:Uridine Triphosphate / Q000378:metabolism
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; C546385:P2RY2 protein, human; C546387:P2ry2 protein, rat; D058910:Purinergic P2 Receptor Agonists; D018048:Receptors, Purinergic P2; D058473:Receptors, Purinergic P2Y2; D000255:Adenosine Triphosphate; D002229:Carbenoxolone; D002118:Calcium; D014544:Uridine Triphosphate