Medicine: Exciting Discovery

High blood pressure causes one-third of all U.S. deaths. Doctors have long considered it one of the most dangerous diseases of 20th Century civilization, and one of the least understood. They may have to modify the latter belief, for a group of British scientists have turned up what looks like a solid clue to the disease. Their discovery: high blood pressure seems to be due to a “short-circuiting” of blood circulation in the kidneys, caused by too much nervous excitement.

Crushed Legs. Like Sir Alexander Fleming’s discovery of penicillin, the high blood pressure discovery was almost an accident. During London’s 1941 air raids, doctors found that victims whose legs had been pinned under timbers or masonry for several hours sometimes died mysteriously of kidney failure. The puzzled doctors called this strange death “crush syndrome.” To find out what a crushed leg had to do with the kidneys, Spanish-born Dr. Josep Trueta and four co-workers at Oxford’s Nuffield Institute for Medical Research* began some blood-circulation experiments on rabbits.

They tied a tourniquet on a rabbit’s hind leg, injected India ink or other opaque fluids into its arteries (to make the blood flow visible) and watched the results by X ray. The experiments soon solved the “crush syndrome” mystery: prolonged pressure on the leg arteries produced spasms of nearby blood vessels, which, among other things, blocked the normal circulation in the kidneys.

Starved Cortex. In the course of solving this puzzle, Dr. Trueta’s research group happened on something with far more exciting possibilities. Physiologists have generally supposed that kidney blood circulation follows a fixed route, with most of the blood circulating through the tiny vessels in the kidneys’ cortex (outer layer). The Trueta research showed that the kidneys have an emergency detour for the blood.

When circulation to the cortex is impeded, the blood bypasses the cortex and flows through bigger blood vessels in the kidney’s medulla or interior (see cut). The cortex, starved for blood and oxygen, deteriorates. Results: 1) the production of urine slows or stops altogether; 2) the anemic cortex apparently secretes a substance (perhaps a hormone) that raises blood pressure throughout the body.

Following up this discovery, Trueta’s investigators found that short-circuiting of the kidney cortex may be produced by many different stimuli. Direct electrical stimulation of certain nerves produced the same result; so did severe hemorrhages, heavy doses of certain hormones (e.g., adrenalin, pituitrin), and injections of the poison secreted by staphylococcus germs. All of these stimuli, the investigators decided, activate nerves which constrict the kidneys’ blood vessels and divert the blood flow from the small vessels in the cortex to the larger ones in the medulla. Lack of blood in the cortex, in turn, raises blood pressure (an automatic adjustment of the body trying to force more blood intp the cortex).

Emotional Storms. Doctors have long been aware that certain types of hypertension (high blood pressure) are connected with kidney disturbances. They have also observed that anger or other emotional storms may raise blood pressure. What the Trueta group demonstrated was the physiological chain of events that leads to hypertension. And they showed that the hitherto unexplained form of high blood pressure known as “essential hypertension,” which accounts for 95% of all cases, stems from the kidneys.

But the kidneys are only the trigger. What pulls the trigger? The Trueta group’s guess: shocks to the nervous system, arising either from injuries or emotional stresses and strains.

Reporting their findings last week in a book published in Britain (Studies of the Renal Circulation; Blackwell Scientific Publications),* Trueta’s group hopefully declared: “We believe that [the primary factors causing high blood pressure] will eventually be found in the central nervous system, even in the human mind itself, and that with their discovery will come a complete understanding of the condition known as ‘essential hypertension,’ affording a new hope for the victims of this disease of civilized man.”

* A British counterpart of the Rockefeller Institute for Medical Research.

* It will be published this fall in the U.S., by Charles C. Thomas. Springfield, Ill.