Stimulation of calcium uptake in PC12 cells by the dihydropyridine agonist BAY K 8644

Methyl 1,4-dihydro-2, 6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)-pyridine-5-carboxylate (BAY K 8644), an analog of dihydropyridine calcium channel antagonists, stimulated 45Ca uptake into PC12 pheochromocytoma cells. Half-maximal stimulation occurred at 80 nM BAY K 8644. Enhancement of uptake was inhibited by cationic and organic calcium channel blockers, but not by tetrodotoxin, which is consistent with an effect on voltage-dependent calcium channels. Stimulation of 45Ca uptake by BAY K 8644 occurred only at elevated concentrations of extracellular K+, suggesting that BAY K 8644 may interact with calcium channels in the open (activated) state.