Expression of P2 receptors by calcifying VSMCs. (a) VSMCs express mRNA for multiple P2 receptor subtypes; expression of the P2X1, P2X2, P2X4, P2X5, P2X6 and P2Y2 receptors is increased up to threefold in calcifying cells compared to control cells. (b) Compared to mineralizing osteoblasts, calcifying VSMCs show increased P2X3 receptor (2.5 fold) expression but reduced levels of the P2X5, P2X6, P2X7, P2Y1, P2Y2 and P2Y13 receptors. Values are mean ± SEM (n = 4), *p < 0.05, **p< 0.01, ***p< 0.001