NIFEDIPINE REDUCES THE INCREASED FREE INT RACELLULAR 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 t his disease. this elevation returns to normal when primary NPT is corr ected In essential hypertension, an alteration in calcium channels all ows a intracellular accumulation of calcium. Aiming to asses if a simi lar mechanism operates in primary HPT, we measured intracellular calci um concentrations using QUIN-2-AM, before and after a 10 mg sublingual dose of nifedipine in 9 subjects with primary HPT, 12 subjects with e ssential hypertension and 17 normal controls. Intracellu lar calcium w as higher in subjects with primary HPT and with essential hypertension than in normal controls (276 +/-56, 343 +/-50 and 113 +/-22 nM respec tively). Among patient with primary HPT, intracellular calcium correla ted with plasma PTH (r= 0.82). Nifedipine reduced intracellular calciu m 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 int racellular calcium and blood pressure correlated significantly (r= 0.6 5 p< 0,03). We conclude that increased intracellular calcium in primar y HPT and essential hypertension seems to depend on an increased inflo w through specific channels. However in primary HPT, this alteration I s related to PTH levels.