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Researchers Probe Possible New Therapy for Hypertension

It would boost, not slow, activity of calcium channels

THURSDAY, Nov. 20, 2003 (HealthDayNews) -- University of Iowa researchers say they've stumbled upon a possible new way to treat high blood pressure.

Calcium channels are proteins that let calcium flow into cells, regulating important cellular functions, most notably muscle cell contraction.

And calcium channel blockers are medications used to slow the rate at which calcium passes into the heart muscle and vessel walls. This relaxes the vessels so blood flows more easily through them, thereby lowering blood pressure.

However, any new medications that might come from this latest research would be designed to increase the activity of calcium channels, rather than block them. So says Kevin Campbell, a professor of physiology and biophysics at the University of Iowa and leader of a research group reporting its surprising finding in the Nov. 21 issue of Science.

It's even more surprising because the calcium channels the researchers investigated weren't supposed to have anything to do with heart muscle cells, Campbell says.

Calcium channel blockers designed to treat high blood pressure target so-called L-type calcium channels.

Campbell and his colleagues were working on a different class of calcium channels -- T-type channels -- that are known to act only in muscles outside the heart.

"We were trying to look at the role of these channels in skeletal muscles," Campbell says. "But when we genetically engineered mice to lack the T-type channels, to our surprise we found that the skeletal muscles worked fine, but the heart muscles became damaged."

Arteries in the mice were found to be misshapen and constricted. Detailed studies by a postdoctoral fellow, Chien-Chang Chen, traced the problem to the smooth muscle cells that surround the blood vessels of the heart. Without the T-type channels, the smooth muscle malfunctioned, Campbell says.

The researchers theorize a drug that would make the heart calcium channels more active could relax blood vessels and lower blood pressure.

"We're working on trying to characterize interacting proteins and understand the mechanism involved, and to better understand ways of activating the channels," Campbell says.

It's too early in the research for pharmaceutical companies to start looking at a potential new class of high blood pressure medications, Campbell says. The long-term outlook is that such medications would provide "maybe a different approach for patients where current calcium channel blockers aren't working," he says.

The finding could also shed light on other heart problems, such as vasospasm, a sudden abnormal constriction of heart arteries, Campbell says.

More information

To learn more about calcium channel blockers, visit the American Heart Association and the Texas Heart Institute.

SOURCES: Kevin Campbell, Ph.D., professor, physiology and biophysics, University of Iowa, Iowa City; Nov. 21, 2003, Science
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