High Pressure, Low Pressure Like Christine Seidman with her studies of cardiomyopathy, Lifton identified a large family with severe high blood pressure. One woman had been hospitalized five times in unsuccessful efforts to control her blood pressure, and many of her relatives had died at young ages from cerebral hemorrhages due to hypertension. By looking at genetic markers present in the DNA of the woman and her siblings and their children, Lifton identified the gene and mutation responsible for the hypertension in the family. By painstakingly searching through DNA from hundreds of individuals in dozens of large families, Lifton has mapped more than a dozen genes that, when mutated, change blood pressure in humans. But not all of these gene mutations cause high blood pressure.
Some mutations actually cause life-threatening forms of low blood pressure in newborns.
Over the past seven years, Lifton has identified mutations in three genes that raise blood pressure, eight genes that lower blood pressure, and another two genes that can increase or decrease blood pressure, depending on whether the mutation activates the gene or shuts it down. The most intriguing aspect of these findings, says Lifton, is that all the mutations affect how the kidney handles salt. Importance of Salt An important function of the kidney is to control the volume of circulating blood and the concentration of salts in the blood. Control of blood volume is required for maintaining proper blood flow and delivery of nutrients to tissues, and tight control of the concentrations of sodium and other ions is necessary for the normal activity of many types of cells. The kidney controls blood volume by regulating the amount of salt it returns to the bloodstream and separately regulates ionic composition by reabsorbing more or less water from the blood.