Studies suggest that some people with essential hypertension may inherit abnormalities of the sympathetic nervous system—the part of the nervous system that controls heart rate, blood pressure, and the diameter of blood vessels. It is estimated that the risk of developing essential hypertension is increased two- to four-fold if one or both parents are diagnosed with the disorder.
Researchers have identified the chromosomes (11 and 18) that house the genes responsible for blood pressure regulation, although narrowing down the range of specific genes involved in hypertension is more difficult.
Genes under intense study are those that regulate a group of hormones known as the angiotensin-reninaldosterone system. This system influences all aspects of blood pressure control, including blood vessel contraction, sodium and water balance, and cell development in the heart.
When blood pressure drops, the kidneys release an enzyme called renin, which initiates a chain reaction to bring blood pressure back up. Renin acts on angiotensinogen (a plasma protein) to produce the hormone, angiotensin I (an inactive form), which is then converted to angiotensin II (an active form of the hormone) by the angiotensin-converting enzyme (ACE). Angiotensin II then stimulates the adrenal glands to release the hormone aldosterone, which decreases kidney sodium excretion, thereby causing blood vessels to constrict. When blood vessels constrict, blood pressure goes up.
Researchers believe that this angiotensin-reninaldosterone system evolved millions of years ago to protect humans. By retaining salt and water and narrowing blood vessels, the body was ensured an adequate blood flow and the ability to repair injured tissue. Over time, however, this system outlived its original protective function and led to serious health complications.
Genevieve T. Slomski PhD, The Gale Group Inc., Gale, Detroit,