1. From the Laboratory of Signal Transduction (K.I., E.M.), National Institute of Environmental Health Sciences, Research Triangle Park, NC; Departments of Physiology and Medicine, The Cardiovascular Research Laboratories (C.P., J.I.G., K.D.P.), David Geffen School of Medicine, University of California at Los Angeles; and Department of Pathology (C.S.), Duke University Medical Center, Durham, NC.