VDR and Hypertension: Vitamin D receptor knock-out mice experience a marked increase in renin expression, plasma Ang II production, and hypertension [33], while, in adequate levels, 25-hydroxyvitamin D inhibits macrophage stimulation [34] and suppresses endothelin-induced vascular smooth muscle cell proliferation [35], both of which modulate endothelial cell function and arterial stiffness.