Inositol trisphosphate accumulation by high K+ stimulation in cultured adrenal chromaffin cells.

Stimulation with high K+ (KCl, 56 mM) of myo-[3H]inositol-prelabelled cells increased Ca2+ uptake and [3H]inositol trisphosphate (IP3) accumulation in a concentration-dependent manner. Nifedipine, a Ca2+ channel antagonist, inhibited high K+-induced [3H]IP3 accumulation and 45Ca2+ uptake with a similar potency. Furthermore, ionomycin (1 microM), a Ca2+ ionophore, also induced 45Ca2+ uptake and [3H]IP3 accumulation. These results indicate the existence of the Ca2+ uptake-triggered mechanism of IP3 formation in cultured adrenal chromaffin cells.