Researchers at Mayo Clinic have identified a previously unknown mechanism that allows the kidneys to regulate water balance without relying on the hormone vasopressin, a discovery that could reshape treatment strategies for millions of people with genetic kidney disease.
The finding emerged unexpectedly during experiments with an old anti-gout medication. The team, led by nephrologist Fouad Chebib, M.D., was testing compounds they expected would worsen polycystic kidney disease. Instead, one substance halted cyst growth in laboratory models, pointing to an entirely separate biological pathway scientists had overlooked.
"It's not every day that you uncover a new way the kidney carries out one of the body's most fundamental processes," Chebib said.
The research, published in the Journal of Clinical Investigation, expands decades of understanding about how kidneys function. Scientists have long attributed urine concentration and water conservation almost entirely to vasopressin. The Mayo team's work reveals the kidneys operate a backup system independent of that hormone.
An Old Drug Points to New Biology
The breakthrough came during routine testing of probenecid, a 1940s medication originally designed to prevent penicillin from being filtered out of the body. Researchers expected it would accelerate cyst formation in their cell models by increasing activity linked to disease progression.
The opposite happened. The drug slowed cyst growth. After repeating the experiments multiple times with the same results, the team realized they had stumbled onto something fundamental.
Investigation revealed how probenecid worked: it altered the way kidney cells handle urate, a molecule typically associated with gout. Inside cells, urate functions as a signaling molecule that triggers movement of water channels to the cell surface. This allows kidneys to reabsorb water and concentrate urine without vasopressin's involvement.
"This demonstrates that the kidney has an additional mechanism to preserve water," Chebib said. "It represents a distinct pathway from what is described in traditional physiology models."
Polycystic kidney disease, a genetic disorder causing fluid-filled cysts to develop in the kidneys, affects roughly 140,000 Americans in its most common form. The condition gradually impairs kidney function, eventually forcing patients toward dialysis or transplant.
Relief From a Difficult Trade-Off
The practical implications are significant. Tolvaptan, the only FDA-approved medication that slows PKD progression, works by blocking vasopressin. However, this creates a severe side effect: patients produce 6 to 7 liters of urine daily. Many wake multiple times each night to urinate, forcing many to abandon treatment altogether.
In preclinical studies and a small clinical trial, adding probenecid to the regimen reduced urine volume by roughly 30 percent while maintaining the drug's disease-slowing benefits. Patients reported waking once per night instead of multiple times, with measurable improvements in quality of life.
"The goal is to preserve the therapeutic benefit of tolvaptan while reducing its burden," Chebib said.
The researchers do not view probenecid itself as a long-term solution. The medication is decades old, affects multiple biological systems, and remains relatively unavailable. Instead, the team plans to use this newly mapped pathway as a blueprint for developing targeted therapies that could address the underlying mechanism without probenecid's drawbacks.
"Probenecid helped us uncover the mechanism," Chebib said. "Our goal is to take this insight and develop therapies designed specifically for this pathway."
For Chebib, the research carries personal weight. His father's PKD diagnosis sparked his interest in the field, transforming a family concern into a research mission aimed at helping patients he has never met.
Author Jessica Williams: "Finding a hidden bypass route in kidney physiology after a century of study shows how much ground-level work remains in medicine, and how the right lab accident can still change treatment for millions."
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