In this study, it has been investigated whether chronic isoproterenol treatments can reproduce the effect of exercise-training on rat epididymal adipose tissue (WAT) .
1. Exercise-training (treadmill running 5 days/week for 8 weeks) reduced the weight-gain, the amount of WAT and the mean daily food intake compared with control. Exercise-training caused hypertrophy of heart and submandibular glands.
2. Chronic isoproterenol-treatments (2.5 mg/100 g body weight/day sc for 6 days) reduced the body weight and the amount of WAT and caused hypertrophy of heart and submandibular glands compared with saline (0.9%) treated rats.
3. Exercise-training markedly increased lipolysis induced by adrenaline (5.5 μM) in WAT segments, and slightly increased lipolysis induced by noradrenaline (5.5 μM) and caffeine (3 mM) . However, lipolysis induced by ACTH (0.5 μM) was markedly decreased.
4. Chronic isoproterenol-treatments markedly increased lipolysis induced by each lipolytic agent.
5. Chronic isoproterenol-treatments mimicked the effect of exercise-training on the weight of various organs, but not on lipolysis induced by ACTH.
6. Chronic isoproterenol-treatments could not reproduce all effects of exercisetraining on rat WAT. Therefore, these results suggest that the response of rat WAT to exercise-training is mediated not only by the beta effect of catacholamine but also by various hormonal factors, and further suggest that it is difficult to reproduce the effect of physiological nerve stimulation only by chronic injections of a neurotransmitter.