Valsartan blocks the angiotensin II receptor type 1 (AT1). This receptor is found on both vascular smooth muscle cells, and on the zona glomerulosa cells of the adrenal gland which are responsible for aldosterone secretion. In the absence of AT1 blockade, angiotensin causes both direct vasoconstriction and adrenal aldosterone secretion, the aldosterone then acting on the distal tubular cells of the kidney to promote sodium reabsorption which expands extracellular fluid (ECF) volume. Blockade of (AT1) thus causes blood vessel dilation and reduction of ECF volume.
