Key points are not available for this paper at this time.
Different effects of injected IP4 and IP3, on membrane Cl− currents were observed in Xenopus oocytes previously microinjected with GH3, cell poly(A)+ RNA. IP3 induced a biphasic current response similar to that induced by TRH, whereas IP4 regularly evoked a monophasic current response consisting of a prolonged inward current with superimposed oscillations. Membrane currents elicited by TRH were enhanced by prior injection of IP4, but not of IP3. In contrast to IP3‐induced membrane currents, those evoked by IP4 were independent of injection depth. Phorbol ester led to enhancement of the initial current after injection of IP3, whereas the current oscillations were greater following injection of IP4. The results indicate that, in Xenopus oocytes, IP4 plays a role different from that of IP3 within the signal transduction pathway initiated by ligand stimulation of a neuropeptide receptor.
Mahlmann et al. (1989) studied this question.