Patients with CKD have an increased risk of developing heart problems, in part because kidney disease can cause their arteries to stiffen. This is thought to occur due to an impaired availability of a vasodilator -- nitric oxide (NO) -- in the blood. The protein endothelin-1 is a vasoconstrictor and opposes the actions of NO, suggesting that drugs that block its effects may help protect CKD patients' heart health. One such drug is called sitaxentan, which blocks endothelin-1's receptor (called the ET_A receptor).

Neeraj Dhaun, MD, PhD (University of Edinburgh, in Scotland) and his colleagues conducted a randomized, double-blind study in 27 patients with CKD to compare the effects of sitaxentan, nifedipine (a blood vessel relaxant), and placebo on kidney function, blood pressure, arterial stiffness, and various heart-related markers.

Among the major findings after six weeks of treatment:

• Placebo and nifedipine did not affect three markers of heart-related problems: blood levels of uric acid; blood levels of asymmetric dimethylarginine (ADMA), a blocker of NO production; and urine levels of endothelin-1.
• Sitaxentan treatment led to statistically significant reductions in all three of these markers.
• Sitaxentan reduced proteinuria (an excess excretion of protein in the urine) to a significantly greater extent than nifedipine. Proteinuria is an indicator of kidney dysfunction.
• Nifedpine and sitaxentan both reduced blood pressure to a similar extent.

"The current study shows, for the first time, that ET_A receptor antagonism selectively lowers novel cardiovascular risk factors in patients with kidney disease independent of blood pressure. These effects were seen in patients already receiving optimal treatment," said Dr. Dhaun. "These findings suggest a potential role for ET_A receptor antagonism in conferring additional longer-term cardiovascular and renal benefits in patients with kidney disease," he added.

Study co-authors include Vanessa Melville, RN, Scott Blackwell, MD, Dinesh Talwar, PhD, Neil Johnston, MSc, Jane Goddard, MD, PhD, and David Webb, MD, FRCP.