Activation of epinephrine and glucagon-sensitive adenylate cyclases of rat liver by cytosol protein factors. Role in loss of enzyme activities during preparation of particulate fractions, quantitation and partial characterization

The role of cytosol components in the loss of rat liver adenylate cyclase activity which occurs during the preparation in particulate fractions from crude homogenates was studied. Epinephrine (5 μM)-, (10 μM)-, and fluoride (5 mM)- stimulated activities of twice-washed particulates were 31%, 58% and 67% of the homogenate activities, respectively. Addition of cytosol (100,000 x g supernatant devoid of adenylate cyclase activity restored these activities to 82%, 88% and 80%. Cytosol also increased particular basal activity from 60% of homogenate activity to 98%.