Lack of Desensitization of Catecholamine-Induced Lipolysis in Fat Cells From Trained and Sedentary Women After Physical Exercise

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Abstract
A study wad designed to assess whether a period of physical exercise (100 min; 60% of maximal aerobic power), known to promote sympathetic nervous system activation, had a functional impact on human fat cell responsiveness to catecholamines and .beta.-agonists. The lipolytic activity of isolated sc fat cells was measured before and after a period of exercise in trained and sedentary women with a similar body mass index values [20.4 .+-. 0.5 (.+-. SE) and 21.3 .+-. 0.5 kg/m2] and an equivalent mean fat cell volume (0.216 .+-. 0.022 vs. 0.278 pm 0.026 nL). Before exercise, compared with those of sedentary women, the adipocytes of trained women had greater lipolytic responsiveness to catecholamines and .beta.-agonists; moreover, dibutyryl cAMP had greater lipolytic efficiency on the adipocytes of the trained women. These results suggest that the differences in responsiveness of the adipocytes from sedentary and trained women are due to functional differences at a postreceptor level of the lipolytic cascade. The lipolytic (.beta.-adrenergic) and antilipolytic (.alpha.2-adrenergic) responses of the adipocytes from both groups did not change after the period of physical activity. These results demonstrate, whatever the physical condition of the subjects, that desensitizaiton of .beta.- and .alpha.2-adrenergic responsiveness does not occur after a period of intense physical activity which promotes physiological activation of the sympathetic nervous system.