1. From the Department of Biochemistry and Molecular Biology (F.K., K.V., A.K., B.J.H.-J., P.L.S.), University of Nebraska Medical Center, Omaha; Department of Pharmacology (N.M., A.L.W.), College of Physicians and Surgeons, Columbia University, New York; and Department of Cardiology (E.D., H.S.D.), Beth Israel Deaconess Medical Center, Boston, Mass.