[Nifedipine reduces the increase of free intracellular calcium in primary hyperparathyroidism: role of calcium channels and PTH].

Free intracellular calcium is increased in primary hyperparathyroidism (HPT) and may be related to the higher incidence of hypertension in this disease. This elevation returns to normal when primary HPT is corrected. In essential hypertension, an alteration in calcium channels allows a intracellular accumulation of calcium. Aiming to asses if a similar mechanism operates in primary HPT, we measured intracellular calcium concentrations using QUIN-2-AM, before and after a 10 mg sublingual dose of nifedipine, in 9 subjects with primary HPT, 12 subjects with essential hypertension and 17 normal controls. Intracellular calcium was higher in subjects with primary HPT and with essential hypertension than in normal controls (276 +/- 56, 343 +/- 50 and 113 +/- 12 nM respectively). Among patient with primary HPT, intracellular calcium correlated with plasma PTH (r = 0.82). Nifedipine reduced intracellular calcium to 173 +/- 36 nM in subjects with primary HPT and to 188 +/- 35 nM in those with essential hypertension. In the latter, the decreased in intracellular calcium and blood pressure correlated significantly (r = 0.65 p < 0.03). We conclude that increased intracellular calcium in primary HPT and essential hypertension seems to depend on an increased inflow through specific channels. However in primary HPT, this alteration is related to PTH levels.