1. From the Nitric Oxide Research Group (L.J.I.), Molecular and Medical Pharmacology, Center for the Health Sciences, University of California, Los Angeles; the Department of Medicine (C.N.), Federico II University of Naples, Naples, Italy; the Department of Medicine (C.N.), University of California, San Diego; and the Evans Department of Medicine (J.L.), Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Mass.