Two Possibly Distinct Prostaglandin E1 Receptors in N1E‐115 Clone: One Mediating Inositol Trisphosphate Formation, Cyclic GMP Formation, and Intracellular Calcium Mobilization and the Other Mediating Cyclic AMP Formation

AbstractProstaglandin E1 (PGE1)‐mediated transmembrane signal control systems were investigated in intact murine neuroblastoma cells (clone N1E‐115). PGE1 increased intra‐cellular levels of total inositol phosphates (IP), cyclic GMP, cyclic AMP, and calcium ([Ca2+]i). PGE1 transiently increased inositol 1,4,5‐trisphosphate formation, peaking at 20 s. There was more than a 10‐fold difference between the ED50 for PGE1 at cyclic AMP formation (70 nM) and its ED50 values at IP accumulation (1 μM), cyclic GMP formation (2 μM), and[Ca2+]i increase (5 μM). PGE1‐mediated IP accumulation, cyclic GMP formation, and [Ca2+]i increase depended on both the concentration of PGE1 and extracellular calcium ions. PGE1 had more potent intrinsic activity in cyclic AMP formation, IP accumulation, and cyclic GMP formation than did PGE2, PGF2α, or PGD2. A protein kinase C activator, 4β‐phorbol 12β‐myristate 13α‐acetate, had opposite effects on PGE1‐mediated IP release and cyclic GMP formation (inhibitory) and cyclic AMP formation (stimulatory). These data suggest that there may be subtypes of the PGE1 receptor in this clone: a high‐affinity receptor mediating cyclic AMP formation, and a low‐affinity receptor mediating IP accumulation, cyclic GMP formation, and intracellular calcium mobilization.