The C-type natriuretic peptide stimulates osteoblastic functions through the B-type natriuretic receptor (NPR-B). In this study, we examined the signaling pathway behind the regulation of NPR-B expression through the prostaglandin E
2 (PGE
2) receptor, EP1 subtype using rat calvarial osteoblasts. A23187 as a Ca
2+ ionophore increased NPR-B expression dose-dependently. PGE
2 or 17-phenyl-ω-trinor PGE
2 (EP1A), an EP1 agonist, increased NPR-B expression, and the potentiating effects were blocked by treating with BAPTA-AM as an intracellular Ca
2+ chelator. Activators of protein kinase C (PKC), 1-oleoyl-2-acetyl-
sn-glycerol, a membrane-permeable diacylglycerol, and 12-
o-tetradecanoyl-phorbol-13-acetate, also increased NPR-B expression, and the potentiating effects were blocked by treating with BAPTA-AM. The treatment of cells with GF109203X, a PKC inhibitor, blocked the PGE
2- and EP1A-induced increase in NPR-B expression. From these results, we concluded that EP1-mediated increase in the expression of NPR-B requires not only Ca
2+ mobilization but also PKC activation through the activation of phosphatidylinositol-specific phospholipase C.
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