ONO-54918-07, a stable prostacyclin analogue, mimics the effect of prostaglandin PGE1 on NG108-15 cells.

The aim of this study was to explore the effect of 0NO-54918-07, a stable prostacyclin analogue, on the current-voltage (IV) curve and the intracellular Ca2+ concentration [Ca2+]i of NG108-15 neuroblastoma x glioma hybrid cells. The IV curve was measured with ramp pulses from -70 to 0 mV, and [Ca2+]i was determined with Fura 2. Bath application of 0.2 muM ONO-54918-07 reversibly increased the holding current at -70 mV by -81.1 +/- 14.8 pA (mean +/- SEM, n = 35) and the slope of the IV curve between -70 and -50 mV by the factor 2.24 +/- 0.24. The effect of 0.2 microM prostaglandin PGE1 was similar (DeltaI (hold) = -96.1 +/- 29.9 pA, g/g (control) = 2.72 +/- 0.44, n = 9). ONO-54918-07 concentrations of 0.04, 2 and 6 microM were also effective. From the dose-response curve, the concentration for the half maximal effect was obtained as 0.054 microM. When cells did not respond to ONO-54918-07, an effect could sometimes be elicited by a ramp pulse or by a second ONO-54918-07 application 30-50 min after the first. The effect of ONO-54918-07 was not affected by pre-treatment with the EP1 antagonists ONO-8713 or SC-51089. However, a 14-40 min pre-treatment with 1 microM RO3244794, a selective prostacyclin receptor (IP) antagonist, abolished the effect of 0.2 microM PGE1. The effect of 0.2 microM ONO-54918-07 vanished completely in the presence of 5 microM RO32446794. ONO-54918-07 and PGE1 produced a slow increase in [Ca2+]i that lasted at least 6 min. Delta[Ca2+]i induced by both substances reached approximately 12% of the peak Delta[Ca2+]i induced by application of bradykinin. In only a few cells, PGE1 produced a brief, transient rise of [Ca2+]i. Using reverse transcriptase polymerase chain reaction, a prominent expression of the IP was detected in NG108-15 cells. It is concluded that ONO-54918-07 mimics the effect of PGE1, supporting the notion that the PGE1 effect on NG108-15 cells is mediated by IP receptors.