Hypertension and Sodium Channel Turnover

Hypertension is an increase of blood pressure to levels greater than normal that arises because of a mismatch between the volume of the vascular tree and the volume of blood. Blood volume depends on total body sodium content, which is a balance between sodium intake and output. Total body sodium is controlled by variable excretion of sodium by the kidneys. To regulate sodium balance, the primary variable that the kidney monitors is not total body sodium, but rather systemic blood pressure. Renal regulation of blood pressure is via the release of the peptide hormone, renin from specialized renal cells. Release of renin ultimately leads to the production of angiotensin II. Angiotensin II increases total peripheral resistance and blood pressure and also leads to an increase in aldosterone. Aldosterone is a steroid hormone that increases sodium reabsorption in the distal nephron by activating epithelial Na channels (ENaCs). Thus, Hypertension is a defect in one of these elements that control total body sodium balance.