Now you know why your wife keeps her blood pressure down even when you keep on sulking during a quarrel at home. According to an interesting research, females have an innate ability to increase levels of anti-inflammatory T cells to keep their blood pressure down.
Called Tregs, the cells are known to help protect us from an excessive immune response, and are naturally associated with lower blood pressures and less organ damage.
Females, at least before menopause, tend to have lower blood pressures than males.
"We think, based on studies in this and other models, that the ability of the female to maintain or upregulate those T regulatory cells is critical to their ability to maintain a lower pressure," said Dr. Jennifer C. Sullivan, professor in the Department of Physiology at the Medical College of Georgia at Augusta University.
In the face of a multipronged front to drive blood pressure up, including a high-salt diet, females are better able to keep their pressure down by increasing levels of a T cell that selectively dials back inflammation.
The cell's levels are known to increase to help maintain a healthy pregnancy, for example, so the immune system does not attack the fetus, which has DNA from both parents.
"This is just a different challenge, but we are using those same protective pathways to do something else good for us," said Sullivan.
Sullivan's work, published in the journal Hypertension, supports the hypothesis that females rely heavily on Tregs for blood pressure control and this mechanism accounts for at least one of the sex differences in that control.
"It's a compensatory response to an increase in blood pressure to help the overall cardiovascular impact," Sullivan said of this innate ability that could provide a promising new hypertension treatment strategy, particularly for women.
Sullivan suspects males and females likely make similar numbers of Tregs -- they have found similar numbers in the spleen, for example -- but differences may be in the recruitment and proliferation to organs key to blood pressure control like the kidneys, one reason she wanted to look specifically at Treg levels there.
Both sexes actually experienced increases in pro-inflammatory T cells, which contribute to infection fighting.
In rats, blood pressure increased significantly in both sexes by day two, but by the end of 21 days of treatment, male blood pressures were significantly higher.
And, females experienced significantly more of the blood pressure-mitigating Tregs along with their lower pressures, the scientists report.
The fact that decreasing Tregs in males did not affect blood pressure may indicate that male blood pressure is not as dependent on this mechanism during normal conditions.
However the clear impact in females supports the hypothesis that females are "highly dependent" on Tregs to maintain their blood pressure.
The hormone DOCA, or deoxycorticosterone acetate, prompts the kidneys to hold onto both more sodium and water, so there is a higher fluid volume in the blood vessels, which drives up blood pressure.
Then, as with some humans, a high-salt diet magnifies the problem and so does the removal of a single kidney.
This DOCA-salt model is a commonly used hypertension model, which provides scientists a good window for when hypertension sets in.
"If we can better understand how and why females are increasing their Tregs that could lead to therapies, potentially for both sexes, to also avoid or treat high-inflammation conditions like autoimmune and cardiovascular disease," Sullivan noted.