DISTRIBUTION OF BETA-ADRENERGIC BINDING IN FRACTIONATED PORCINE ADIPOCYTES

1. The subcellular distribution of the porcine adipocyte beta-adrenerg ic receptor was studied in fractionated adipocytes. 2. The 30,000 g pe llet obtained from hypotonically lysed cells contained membrane vesicl es and mitochondria; it yielded approx 200-300 fmol dihydroalprenolol- bound receptors/mg protein. 3. Activity was increased to about 1000 fm ol/mg protein after isolation of a plasma membrane fraction on a Perco ll gradient. 4. The 5'-nucleotidase, succinate dehydrogenase and lacta te dehydrogenase activities were usually enriched in compartments diff erent from the ligand-binding activity. 5. Activity of porcine adipocy te 5'-nucleotidase, a purported plasma membrane marker enzyme, was not distributed in the same manner as the beta-adrenergic receptor.