Modulation of calcium mobilization by guanosine 5'-O-(2-thiodiphosphate) in Xenopus oocytes.

We investigated the effect of intracellular loading of the non-hydrolyzable guanosine 5'-diphosphate analogue GDPsS on calcium mobilization by IP3 and on calcium influx in Xenopus oocytes. Assayed by two electrode voltage-clamp recording, GDPsS-loaded oocytes demonstrated a marked augmentation of the fast component of the response to IP3 injection, an attenuation of the slow component and an increase in membrane calcium permeability. These effects on calcium mobilization suggest that gdpβs may facilitate calcium translocation both across the plasma membrane and between different intracellular calcium pools.