Genetic armor inherited from ancient Native American ancestors may be protecting Mexican-Americans from heart disease and high blood pressure, a San Antonio research team says.

The Native American genetic theory is one being explored as researchers search for an explanation of why Mexican-American men have slightly lower rates of heart disease and high blood pressure than do Anglos.A puzzling aspect, they said, is that it is occurring despite a greater incidence of obesity, 60 percent more than Anglos, and a predominance of other factors among Mexican-Americans that generally trigger heart and blood vessel disorders.

"The point here is not that it is less, but that the expectation was that it would be higher," UT Health Science Center Professor Dr. Michael P. Stern said Friday.

Stern on Saturday presented the initial findings in the medical mystery at a seminar on high blood pressure at the San Antonio American Heart Association Chapter.

Figures drawn from the long-range San Antonio Heart Study have shown that 7.3 percent of lower middle-class Mexican-American men have high blood pressure compared to 10 percent of Anglo men of similar status. Additionally, heart disease strikes 15 percent fewer Mexican-American men than Anglo men, once again despite proportionately more obesity, diabetes and other factors that would seem to predispose them to heart problems.

"Something is going on in all of this, but I don't have a clear answer," Stern said.

He believes an interesting solution "could be" the inheritance of some protective genetic trait from Native American peoples, some of whom also show numerous factors suggestive of higher amounts of heart and blood vessel disorders, but who actually have fewer such problems than do Anglos.

"Mexican-Americans have a long list of risk factors for high blood pressure," said Stern, head of a precedent-setting heart study that five years ago discovered Mexican-Americans here are three to five times more likely to have the blood-sugar disorder diabetes than are Anglos.

"Therefore you would predict that they would have more hypertension (high blood pressure)," Stern said. "But lo and behold, they have less hypertension."

One of numerous studies in which he participated compared Mexican-American rates of obesity with those of the Pima Indians of the Southwest. These Native Americans also have much higher rates of diabetes than Anglos, but have as much as 40 percent less heart disease.

The Pima's lower rate of heart disease is occurring despite even higher rates of obesity than Mexican-Americans.

For example, in the general U.S. population, 15.6 percent of the people suffer from obesity. Among the Pima Indians, 43.1 percent suffer from obesity, and obesity afflicts 25.8 percent of Mexican-Americans.