Scientists from the University of Maryland School of Medicine and a Michigan pharmaceutical firm said today they have isolated and identified a hormone they believe promotes the development of high blood pressure, a condition affecting some 60 million Americans.
If they can now discover how the hormone is made, the scientists said, they may be able to block its production and, as a result, possibly lower blood pressures that are too high.
"Anything that interferes with the secretion or action of the hormone might be beneficial in the treatment of high blood pressure," said Dr. Mordecai P. Blaustein, professor and chairman of physiology at the university.
To their surprise, after processing hundreds of gallons of human blood plasma over eight years, the researchers found that the newly discovered hormone -- human ouabain -- appears to be structurally identical to a plant-derived digitalis-like substance called ouabain (pronounced WAH-buyin').
"In every way that we have been able to test so far, the human hormone works the same way as ouabain, the plant steroid," said Blaustein. "This was a startling revelation because we had no idea that humans are capable of making ouabain."
Ouabain slows the activity of a process -- called a "pump" -- that normally moves sodium out of blood vessel cells. It also indirectly stimulates the blood vessel cells to contract, "and that's the problem in hypertension," the researcher said in an interview.
"The ouabain stimulates the cells too much and they contract so much that in certain individuals the blood pressure goes up," he said.
Blaustein and colleagues at the University of Maryland and at Upjohn Co. laboratories in Kalamazoo, Mich., presented their findings in a series of reports at the 44th annual conference of the American Heart Association Council on High Blood Pressure Research.
The sessions opened last night and continue through tomorrow at the Hyatt Regency Hotel here. More than 80 research reports, poster presentations, special lectures and panels have been scheduled.
At the same conference, Dr. John M. Hamlyn, an associate professor of physiology at the University of Maryland School of Medicine, reported that in humans and cows, the adrenal glands are a probable source for ouabain.
The team also has developed a test that detects high levels of the hormone in blood, which might prove useful in predicting who will have high blood pressure later in life.
But, hundreds of additional people -- those who have been diagnosed with high blood pressure but who have not been treated -- must be tested to confirm the role the researchers believe the hormone is playing in the development of high blood pressure.
With luck -- and some hard-to-get grant money and personnel -- the test might be available in doctor's offices in about three years, Blaustein said.
"We've applied for some grants and, obviously, there is going to be a large commercial interest in this," he said, declining to be more specific. "We're really anxious to get this out in the public as quickly as possible."
Blaustein's theory that a sodium pump-inhibiting hormone exists stemmed from his pioneering research that included studies of muscle cells from barnacles and rabbit arteries. The search for the hormone accelerated in 1982, when Hamlyn, Blaustein and their associates published evidence that a sodium pump-inhibiting hormone exists in the blood plasma of patients with high blood pressure.