High blood pressure is the most common biological condition that predisposes to serious diseases and it is readily treatable with meds. It triggers heart attacks and strokes that result in more than half of the deaths, more than all cancers together. What about this blood pressure, anyway.
The kidneys are among the important organs which keep us alive. They are all animal’s waste disposal units working 24 hours a day without rest. Their failure without medical treatment is devastating. To do its work the kidneys receive 25% of the bodies’ blood flow. They require over a quart of blood a minute! This is substantially more than goes to the heart or even to our brain. This substantial kidney blood flow must be regulated because the kidney’s “cleaning stations” require blood to pass through at sufficient pressure to continue flow in very minute vessels. I mention this to make the following description of the process that the kidneys use to insure adequate pressure reasonably necessary. IT IS NECESSARY!
Angiotensinogen (-sinogen means precursor in biology) is a protein secreted by the liver. It is similar to the foreman in a power company, patrolling ready to act. Renin (probably derived from renal, cute) is an enzyme released from the kidney when nerve cells sense that more blood flow is needed. Renin slices off the active part of angiotensinogen, angiotensin I, which undergoes alteration by another enzyme angiotensin-converting-enzyme (ACE) to become angiotensin II, a powerful constrictor of blood vessels and also causes release of aldosterone in addition from the adrenal glands. Aldosterone causes salt to be reabsorbed which increases blood volume and raises blood pressure. Fully activated angiotensin II packs a double whammy!
I have several different points to make before you think me punctilious for offering info you may think totally unnecessary. First, it is but one of many examples of why I believe Evolution is secondary, not primary in the present state of life. Before is the simple version of blood pressure control. The angiotensinogen molecule formed by the liver is composed of over 400 building blocks assembled in the correct order, then all the rest of the process happens.
Next, because of the multiple steps involved, six different classes of drugs may be employed to lower blood pressure by interrupting or slowing each step in the chain of reactions which produce hypertension. So, unlike many other conditions, blood pressure can be lowered satisfactorily and complications may be avoided by altering meds when needed. Biology at work is magnificent indeed.