Parathyroid hypertensive factor appears to be a new circulating pressure factor. Its vasoconstrictive effect and influence on calcium channels in the vascular smooth muscle cells was demonstrated. Parathyroid origin was proved in the spontaneously hypertensive rats. In the parathyroid tissue of those rats, a "new type of cells" was identified at the electron microscopic level.

        Key words: parathyroidal hypertensive factor, PHF, calcium channels, spontaneously hypertensive rats, hypertension