In vivo effects of calcium entry blockers on human parathyroid adenoma cells with special reference to calcium sensing ability and the hormone secretion

We evaluated the effects of calcium-entry blockers on parathyroid hormone (PTH) secretion by human parathyroid adenoma cells in vitro. Nifedipine and barnidipine inhibited PTH secretion, while diltiazem had no significant effect. Cytosolic calcium concentrations were measured by use of the calcium-sensitive fluorescent dye fluo-3 with confocal laser scanning microscopy. Nifedipine increased the cytosolic concentration of calcium, whereas diltiazem decreased it. Results suggest that, in parathyroid adenoma cells, regulation of PTH secretion with respect to intracellular calcium concentration would be maintained despite differing response of intracellular calcium concentration following exposure to calcium-entry blockers.