Lucky About Renin


Our blood nourishes and oxygenates every cell in our body. But that blood could not reach those cells without a pressure behind it, forcing it through our body. Just as important, if that pressure decreases too much and for too long – minutes in some cases for the brain and heart – death will occur.

So, it just so happens, through a series of physiological events far too complicated for our purposes here, the body maintains blood pressure within a relatively narrow range. One of the ways it does this is through a hormone (renin) produced by the kidneys.

For the sake of simplicity, when the kidneys sense a decrease in circulating blood volume (a low circulating blood volume translates into low blood pressure), they secrete renin. Renin travels through the blood system to the liver where it is converted to a substance called angiotensin 1. Angiotensin 1 then travels to the lungs where it is converted into angiotensin 2 (A2).

Here is where it gets down to the business of increasing blood pressure. (Renin – part of the Renin-Angiotensin-Aldosterone System does other things to increase blood pressure, but let’s focus now only on blood volume).

Through another series of complex steps, A2 travels to the pituitary gland in the brain where it causes the release of a hormone called vasopressin (also called anti-diuretic [anti-urinate] hormone). Vasopressin travels back to the kidneys, causing them to conserve water and decrease urine production.

A2 also travels to the adrenal glands situated on top of the kidneys, causing them to secrete another hormone called aldosterone. Aldosterone also circulates back to the kidneys, causing further conservation of water and a decrease in urine production. Increased retention of water leads to an increase in circulating blood volume – leading to an increase in blood pressure.

Of course, if all this water retention continued unabated, our blood pressure would eventually go through the proverbial roof and we’d die of severe high blood pressure – kind of like what happens to a water balloon when you continue to force water into it. It explodes.

Now here is the point: At some point in our eons-old evolution, and through a series of highly complex and sophisticated mechanisms, our evolutionary ancestor suddenly and simultaneously developed the Renin-Angiotensin-Aldosterone System to maintain their blood pressure within a narrow range.

Or, God suddenly and simultaneously set those complex and sophisticated mechanisms into motion with the creation of the first human.

(I've included a simplified schematic of the Renin-Angiotensin-Aldosterone System)

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