Swine Adipocytes Research Articles

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.

Lipolytic activity of swine adipocytes

Lipolysis in isolated swine adipocytes was stimulated by epinephrine, dibutyryl cyclic AMP, and weakly by adrenocorticotropin but not by glucagon or cyclic AMP. Theophylline, a phosphodiesterase inhibitor, stimulated lipolysis and greatly enhanced the activity of adrenocorticotropin. The epinephrine-stimulated lipolytic activity, expressed on a tissue or cell volume basis, was greatest at 25 days postpartum, whereas, expressed on a cell basis, the activity was maximal at day 80. Regardless of the mode of expression, the activity at day 150 was low. Cells from younger animals were more sensitive to epinephrine than cells from older animals.