Abstract
Bone marrow stromal cells have hardly been studied physiologically, although they are given attention to as well as hematopoietic stem cells. We investigated intracellular calcium signals in rat bone marrow stromal cells using fura-2 AM. UTP, an agonist of P2Y2 receptor (G protein-coupled purinergic receptor) induced an increase in intracellular calcium concentration. An immunohistochemical study showed the expression of P2Y2 receptors in these cells. Depletion of intracellular calcium stores with thapsigargin induced store-operated calcium entry (SOC). These calcium responses changed depending on the cell density. The SOC-induced calcium increase was largest at low density, whereas UTP-induced calcium increase was largest at high density. Releasable calcium contents were constant regardless of cell density. UTP induced calcium oscillation, of which frequency was highest at medium density. These cell density-dependent differences in calcium responses may suggest cell growth-dependent changes in calcium signaling mechanism. [Jpn J Physiol 55 Suppl:S124 (2005)]
