Infusion of bovine parathyroid hormone1-34 attenuates the pressor response to angiotensin II in spontaneously hypertensive rats.

Parathyroid hormone, long known to be important for calcium homeostasis, also has potent vascular effects. In the past, pharmacologic doses of parathyroid hormone or its active amino-terminal fragment (PTH1-34) were necessary to demonstrate vasoactivity. We assessed the vascular effects of physiologic doses of infused synthetic bovine PTH1-34 (15 U/hr or 1.5 micrograms/hr) on the pressor response to angiotensin II. PTH1-34 attenuated the pressor response (p less than 0.005) to one to 100 nanograms of angiotensin II in both Aoki-Okamoto spontaneously hypertensive and normotensive Wistar Kyoto rats. There was no difference in response to either PTH or angiotensin II between strains, and at the lower doses of angiotensin II, PTH1-34 dampened the pressor response by as much as 33%. These results suggest that endogenous PTH may modulate systemic blood pressure and regional vascular resistance. In various states of parathyroid gland stimulation, the peptide may exert physiologically important vascular effects.