Two kinds of drugs used to treat high blood pressure appear to work together on the molecular level in the body, says a report that might impact the treatment of both high blood pressure and heart failure.
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The drugs are beta blockers, which act on receptors that control the amount of blood delivered to the body at times of stress, and angiotensin-converting enzyme (ACE) inhibitors, which act on receptors that regulate growth of heart muscle.
Simplified treatment of hypertension
There has been evidence that these two receptors act as a pair, holding hands in the cell membrane to form what we call dimers, says study author Dr Howard Rockman, a professor of medicine at the US Duke University Medical Center whose report appears in the Sept. 9 issue of Circulation. But until now there has been no evidence that if, say, a beta blocker is used as a therapy, it not only blocks one receptor but blocks the pair.
If human studies confirm the finding, it could simplify treatment of high blood pressure, which now usually requires people to take two drugs, Rockman says. Use of one drug is probably more potent than what we currently believe, so we might be able to get the most out of one medication, he explains.
Steps taken
A first step toward the finding was to grow mouse heart cells in laboratory cultures. When a beta blocker was added to the cultures, the cells had a markedly weaker than expected reaction to a chemical that stimulates angiotensin receptors, showing that the beta blocker was affecting those receptors.
In a second step, mice were first given an angiotensin receptor blocker, followed by a chemical that activates beta receptors. Those beta receptors remained inactive, just as would happen if they were exposed to a beta blocker. That shows direct receptor-receptor interaction, Rockman says.
Theories put to the test
Now comes the interesting part. Since both those blockers act on each other's receptors, we could start a patient with the less difficult of the two medications, Rockman says. In some patients, beta blocker therapy is difficult to initiate because of instability. In theory, we could use the other agent, an angiotensin receptor blocker to start, so that the person becomes more stable when beta blocker therapy begins.
That theory will soon be put to the test in a human trial - of treatment not of high blood pressure but of heart failure, in which an ailing heart becomes progressively enlarged and loses its ability to pump blood.
Beta blockers now are the first-line choice of drugs for heart failure, Rockman says. It would be easy to test an ACE inhibitor in a trial as a first-line drug for heart failure.
Plans for such a trial at Duke have been drawn up, he says. The trial will include hundreds of persons with advanced heart failure, he says.
In the longer run, it might be possible to tailor drug treatment for heart failure or high blood pressure to an individual's specific receptor activity, with a blood test that hopefully would show which treatment would be best for that individual. - (HealthDayNews)
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