The postmitochondrial
supernatant was centrifuged 60 min at 100,000 g. The microsomal
pellets were surface washed with SI buffer (25 mM sucrose and
25 mM imidazole, pH 7.2 [SI]) and stored frozen in liquid N2. The
supernatant (liver cytosol) was stored frozen at -20°C. Rat liver microsomes
and cytosol were prepared as described by Suttie et al. (9).