1. From the Cardiovascular Research Center and Department of Physiology (A.H., K.K., S.H., K.E., A.T., K.I., L.J.S., M.V.A., S.E.), Temple University School of Medicine, Philadelphia, Pa; Department of Biochemistry (G.D.F.), Vanderbilt University School of Medicine, Nashville, Tenn; Department of Biochemistry and Molecular Biology (W.T.G.), University of South Alabama, College of Medicine, Mobile, Ala.