Preparation, characterization, and insulin sensitivity of isolated swine adipocytes: comparison with adipose tissue slices.

The technique of Rodbell (J. Biol. Chem. 239: 375) was modified considerably in order to isolate swine adipocytes without rupturing large cells. Cell size and diameter distributions were the same for adipocytes fixed with OsO4 following isolation with collagenase and adipoctes liberated from OsO4-fixed adipose tissue slices. Lipogenic rates were greater for isolated adipocytes compared with thin adipose tissue slices at low (0.5 mM) and high (10 mM) glucose concentrations (cells = 307 and 1100; slices = 139 and 744 nMoles glucose leads to lipid/10(6) cells/hr for 0.5 and 10 mM glucose, respectively, P less than 0.001). Similar differences were found for glucose oxidation. Sensitivity to insulin was determined by measuring the stimulation of lipogenesis and glucose oxidation in the presence of 0, 1, 5, 25, and 100 ng/ml of purified porcine insulin at low (0.5 mM) and high (10 mM) glucose concentrations. Relative to basal incubations, the addition of insulin caused similar increases in glucose oxidation and lipogenesis for isolated adipocytes and adipose tissue slices when glucose concentration was 10 mM. These results indicate 1) that isolated swine adipocytes can be prepared without alterations in cell size or diameter distribution, and 2) that isolated adipocytes have higher rates of glucose oxidation and lipogenesis from glucose even though they retain a similar in vitro sensitivity to insulin.