Parathyroidectomy lowers blood pressure independently of changes in platelet free calcium

Several lines of evidence indicate that the parathyroid gland plays a role in blood pressure regulation. To examine whether the attenuation of the development of hypertension by parathyroidectomy is associated with modifications in cellular calcium metabolism, intracellular free calcium was determined in fura-2-loaded platelets of spontaneously hypertensive rats after parathyroidectomy. Parathyroidectomy decreased systolic blood pressure (146 +/- 8 versus control 160 +/- 5 mmHg, n = 8 and 9, respectively; P less than 0.05) and serum ionized calcium (0.81 +/- 0.08 versus 1.28 +/- 0.04 mmol/l; P less than 0.01). However, no effect of parathyroidectomy on basal intracellular free calcium was detected (63.1 +/- 5.5 versus 65.0 +/- 5.1 nmol/l). Furthermore, there were no differences in the intracellular free calcium responses to thrombin in the presence and absence of external calcium, intracellular calcium discharge capacity or calcium extrusion from the cytosol. These results indicate that parathyroidectomy lowers blood pressure independently of alterations in platelet calcium handling.