NEW YORK, March 11 (Reuters) -- A new study suggests that high blood pressure rapidly ages blood vessels -- the internal equivalent of premature crow's feet or strands of gray hair. As people age, blood vessels stiffen and lose their ability to contract and relax, and generally respond to the body's need for blood -- a process speeded up in those with high blood pressure, according to a report in the American Heart Association's journal, Hypertension.
The finding helps explain why hypertension increases the risk of heart attack and stroke -- "aged" blood vessels may be unable to respond to an increased demand for blood in the heart or brain.
According to lead study author Dr. Stefano Taddei, of the University of Pisa in Italy, the aging process involves changes in the endothelium, cells lining blood vessels. These cells, when healthy, can respond to triggers and relax or contract blood vessels.
For example, when activated by specific chemicals, such as acetylcholine, endothelial cells release nitric oxide, "a powerful relaxing agent," according to the report. In the new study, Taddei and colleagues found that people with high blood pressure were less likely to respond to acetylcholine than those with normal blood pressure, and as people got older, they were even less likely to respond to the drug.
In people over the age of 30 with normal blood pressure, an amino acid called L-arginine -- which can be converted to nitric oxide in the body -- helps restore the reaction to acetylcholine to that found in a 20-something person. The amino acid is still effective up to about age 60. After age 60, L-arginine "still increased but did not normalize the response to acetylcholine," write the researchers.
However, in those with high blood pressure, the amino acid's effectiveness fades earlier, in the mid-40s. People with hypertension also have factors that trigger endothelium to constrict blood vessels in middle-age or sooner, while such factors don't cause problems in those with normal blood pressure until old age.
The researchers made the discovery by measuring blood flow in the arms of 43 people, aged 18 to 73, with normal blood pressure and 47 patients, aged 20 to 72, with high blood pressure.
"Taken together, these findings indicate that mechanisms causing endothelial dysfunction are the same in aging and essential hypertension, although they appear at a younger age in hypertensive disease," Taddei wrote. The study suggests that "impaired endothelium-dependent (blood vessel dilation) in essential hypertension could be a mere acceleration of the changes seen in aging."
SOURCE: Hypertension (1997;29:736-742)
