A clonal prostaglandin-responsive cell line (RDP 4-1) derived from rat dental pulp

The RDP 4-1 cell line was established from isolated rat dental pulp and cloned with limiting dilution in 96-multiwell plates. Despite their fibroblast-like appearance, RDP 4-1 cells required more than 5% (v/v) heat-inactivated fetal calf serum to maintain the cell growth and function. Type I collagen, but not type II and type III collagen, was immunocytochemically detected in the cells in subconfluent cultures. Prostaglandin E2 (PGE2, 5 ng/ml-5 micrograms/ml) dose-dependently increased cAMP accumulation, while prostaglandin F2 alpha (PGF2 alpha, 5 micrograms/ml) slightly increased it, in the presence of 0.1 mM isobutylmethyl xanthine. PGE2 (5 ng/ml-5 micrograms/ml) also stimulated phosphoinositide hydrolysis to produce inositol phosphates (IPs) in a time- and dose-dependent manner in the presence of 10 mM LiCl. PGF2 alpha was a more potent stimulator of phosphoinositide hydrolysis. Both prostaglandins increased cytoplasmic free calcium, independent of the level of extracellular calcium. Prolonged exposure (48 h) of the cells to PGE2 at higher concentrations (greater than or equal to 0.5 micrograms/ml) increased DNA synthesis. In these RDP 4-1 cells, thus, PGE2 receptors appeared to be associated with both cAMP and IPs-Ca2+ signaling systems, and that PGF2 alpha receptors are poor stimulators of the former but more potent ones of the latter. Our results suggest that both prostaglandins have some roles in regulating dental pulp metabolism.