Parathyroids, thyroid and development of hypertension in SHR.

Parathyroid glands play a significant role in the development of hypertension in spontaneously hypertensive rat (SHR), like in deoxycorticosterone acetate (DOCA) + NaCl model. Parathyroidectomy (PTX) performed after weaning delayed systolic blood pressure (SBP) increase and slowed heart rate (HR) in SHR for 42 weeks. These changes could not be attributed to decrease of serum calcium in PTX animals since supplementation of calcium, rendering serum calcium normal, did not reestablish SBP and HR to those of sham SHR. Moreover, in the thyroparathyroidectomized (TPTX) animals SBP and HR were increased by autotransplantation of parathyroids. When hypertension was established (week 15), PTX produced no more changes on cardiovascular parameters measured. These data clearly indicate that independent of thyroidectomy, PTX leads to a lesser degree of hypertension in young SHR, but was without effect on established hypertension. In conclusion, parathyroid glands are required for total development of the hypertensive process in SHR.