| Popis: |
The effects of tetracycline on the metabolism of isolated rat white fat cells were examined. Tetracycline at a concentration of 0.05 mg/ml inhibited lipolysis due to 0.075 or 0.15 muM norepinephrine, but not that due to adenosine deaminase, theophylline, dibutyryl cyclic AMP or 1.5 muM norepinephrine. Higher concentrations of tetracycline (1 mg/ml) inhibited lipolysis due to all added agents except dibutyryl cyclic AMP. The accumulation of cyclic AMP after 5 minutes incubation with 0.15 muM norepinephrine plus adenosine deaminase was inhibited by 0.05 mg/ml of tetracycline. The large rise in cyclic AMP accumulation at 5 minutes due to 1.5 muM norepinephrine in the presence of 100 muM theophylline was only slightly inhibited by 0.05 or 0.1 mg/ml of tetracycline. Tetracycline at 1 mg/ml did markedly inhibit cyclic AMP accumulation due to all added agents. The stimulation of adenylate cyclase activity of fat cell ghosts by norepinephrine or fluoride was inhibited by 0.05 mg/ml or greater concentration of tetracycline. Insulin-stimulated glucose oxidation by fat cells was inhibited by 1 mg/ml of tetracycline. These results suggest that the anti-lipolytic action of tetracycline on rat fat cells is secondary to inhibition of cyclic AMP accumulation. |
