1. Nuclear Medicine Research Laboratory, Veterans Administration Medical Center (R.R.C.), San Francisco, California
2. Liver Center (R.R.C., B.F.S., N.L.), Department of Medicine, University of California, San Francisco, California 94143-0538
3. The Department of Pharmaceutical Sciences, University of Brasilia (L.A.S., R.C.J.R.), Brasilia, DF Brazil
4. University of California (S.W.P.), Davis, California 95817
5. The Metabolic Research Unit (J.D.B.), University of California, San Francisco, California 94143-0538
6. Gastroenterology Division (B.F.S., N.L.), University of California, San Francisco, California 94143-0538