Inositol 1,3,4-trisphosphate and inositol 1,3,4,5-tetrakisphosphate evoke an inward current in NG108-15 cells, suggesting they do not release sufficient Ca2+ to activate Ca2+-dependent K+ currents unlike inositol 1,4,5-trisphosphate.
Distinguishes IP3 isomer effects on membrane currents in NG108-15 cells; leaves open their roles in cardiovascular signaling.
Iontophoretic injections of inositol 1,4,5-trisphosphate inside neuroblastoma X glioma NG108-15 hybrid cells evoked an outward K+ current across the outer cell membrane, probably activated by the release of intracellular Ca2+. No such current was produced by equivalent intracellular injections of inositol 1,3,4-trisphosphate or inositol 1,3,4,5-tetrakisphosphate. Instead, these compounds evoked an inward current with a reversal potential of about -20 mV, and which may therefore be due to a non-specific cation conductance. This suggests that these derivatives are unable to release sufficient Ca2+ to activate the Ca2+-dependent K+ current in these cells.
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Higashida et al. (1986) studied this question.
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