Also here, epithelial cells, unlike those lining the vasculature, work at transporting cells important to kidney function. The transporting cells are found in the medulla, an area of the kidney vital to determining whether sodium is excreted. These cells have receptors for endothelin that tell nitric oxide synthase to make nitric oxide which, in turn, tells the sodium channels that allow sodium to be reabsorbed by the body to close. That enables the sodium to be excreted in the urine. Our big hypothesis predicts that when you eat a lot of salt, you have an increase in the amount of endothelin made.
Tests indicate they are on the right track.
The researchers are giving antagonists to block endothelin receptors. We also have shown in those same animals that nitric oxide goes up. To get a better grip on still unknown factors that affect blood pressure, they are using advanced technology that looks at gene expression to examine genetic material from the medullas of a special strain of salt-sensitive rats and comparing those findings to normal rats. It turns out that in excess of 70 genes are up-regulated in the normal animals, but in the animals that become hypertensive, there is only one gene that is turned on. So maybe the way to think about this is that the problem is not all these things that get turned on, maybe it s the things that don t get turned on.