Women’s kidneys respond to eating a lot of salt by making more endothelin-1—a substance that helps flush out salt—but men’s kidneys don’t make more of it, even when they eat the same amount.

When women who are healthy and not menopausal eat a lot more salt for 10 days, their kidneys release more of a substance called endothelin-1 to help flush out the extra salt—but men’s kidneys don’t do this same thing.

In rats, male kidneys make more endothelin-1 when they eat salt—but in humans, it’s the opposite: female kidneys make more. This shows we can’t just assume animal results apply to people.

When mice with lupus eat a lot of salt, their kidneys release more of a chemical called endothelin-1, but they also make less of the receptor that makes blood vessels tighten — which might help protect their blood pressure.