The purpose of this study is to see if a naturally-occurring hormone called erythropoietin changes the action of platelets in the blood. Erythropoietin is made by the kidneys to stimulate red blood cell production to prevent anemia. Platelets are small cells in the blood that help clot blood in case of injury. Platelets also sometimes form blood clots in blood vessels that may cause heart attacks. This study is trying to determine whether erythropoietin increases the clotting action of platelets. Information on erythropoietin in healthy subjects may eventually help in the treatment of patients with heart attacks.