Take a kidney out of the body and it still knows how to filter toxins from the blood.
But all bets are off in the face of high blood pressure.
"How does the kidney know how to do it and why does it break in hypertension?" says Dr. Edward W. Inscho, physiologist in the Medical College of Georgia Schools of Medicine and Graduate Studies.
The kidneys filter about 200 quarts of plasma daily, eliminating about two quarts of waste product and extra water as urine, according to the National Institute of Diabetes and Digestive and Kidney Diseases. But the complete physiology remains a mystery.
He challenged colleagues to fill in important blanks in how this process works normally and how to make it work better in disease during the Sept. 19 Lewis K. Dahl Memorial Lecture at the 62nd High Blood Pressure Research Conference and Workshop in Atlanta.
One thing is clear: Hypertension takes a serious toll on the kidneys and damaged kidneys worsen hypertension. Dr. Inscho believes the kidneys' million hard-working filters, or glomeruli, are direct victims of high pressure. His research focuses on the minute arteries, or arterioles, that feed blood into each of them. These afferent arterioles are responsible for keeping blood pressure at a comfortable 60 mmHg inside glomeruli. At a healthy blood pressure of 120/80 mmHg, blood enters the artery at a mean pressure of 100 mmHg, but higher pressures mean the arterioles must work even harder to reach the 60 mmHg target. They seem up to the task at least initially, contracting to make it harder for blood to pass and reducing pressure in the process. "We want to know how it does that," Dr. Inscho says as he watches the near instantaneous contraction.
He thinks he may at least know the messenger. The first reaction to high pressure actually is for the small vessel to stretch. That stretch prompts smooth muscle cells on the vessel wall to release ATP, a common molecule known
|Contact: Toni Baker|
Medical College of Georgia