Effects of Rosiglitazone on Endothelium-Dependent Vasodilation and on Endothelin Activity in Patients With Essential Hypertension and in Patients With Hypercholesterolemia

Detailed Summary

Cells in the lining of blood vessels produce various substances that cause the vessels to dilate (relax) and constrict (tighten), thereby regulating blood flow. In patients with high blood pressure and high cholesterol, the blood vessels do not dilate properly. This study will investigate the effects of rosiglitazone-a drug used to improve the action of insulin in diabetic patients-on blood flow by examining its effects on endothelin (a substance that causes vessel constriction), and other substances produced by the vessel-lining cells. Adults with blood pressure recordings of 140/90 mmHg or higher on at least three separate days or with a blood cholesterol level of at least 240 mg/dl may be eligible for this study. Candidates will be screened with a medical history and physical examination, blood pressure recordings, blood and urine tests. This "crossover" study involves two separate treatment periods; that is, participants will take either rosiglitazone or placebo (an inactive look-alike pill) once a day for 8 weeks, then no drug for 4 weeks, and then the alternative treatment for the next 8 weeks. Patients will continue to take their high blood pressure medicines during the first 6 weeks of each treatment period. They will stop the medication 2 weeks before the following procedures, which are done at the end of each 8-week treatment period: Strain gauge plethysmography-A small catheter is placed through a needle into an artery at the bend of the arm for measuring blood pressure and drawing blood samples during the study. Pressure cuffs are placed on the wrist and upper arm, and a strain gauge (a rubber band device) is placed around the forearm to measure forearm blood flow. When the cuffs are inflated, blood flows into the arm, stretching the strain gauge at a rate proportional to the flow, and the measurement is recorded. Small doses of four drugs-acetylcholine, bradykinin, sodium nitroprusside and BQ-123-are given through the catheter. Acetylcholine slows the heart rate. Bradykinin stimulates the release of a substance that causes blood vessels to dilate and can lower blood pressure. Sodium nitroprusside causes blood vessels to dilate and is used to treat high blood pressure and heart failure. BQ-123 blocks the blood vessel-constricting activity of endothelin. Brachial ultrasound reactivity study-A baseline ultrasound image (picture produced using sound waves) of the brachial artery (artery located at the bend of the arm) is taken and blood flow measurements are recorded. Then, a pressure cuff is placed around the upper forearm, inflated for 5 minutes to stop blood flow to the forearm, and then released. Images of the artery and flow measurements are repeated. After a 15-minute rest, new baseline images are taken and flow measurements obtained. A small amount of nitroglycerin is then sprayed under the tongue and after 3 minutes, blood flow measurements and brachial artery images are recorded once more.

Study Details

Timeline