Plasma levels of catecholamines and lipolysis during starvation in growing pigs

The aim of this study was to clarify the triggering mechanism of lipolysis in adipose tissue during feed withdrawal in pigs. Evaluation of blood samples drawn via an intravenous catheter from 10 growing pigs fasted for 60 h demonstrated, in addition to a haemodilution, a significant rise in plasma levels of non-esterified fatty acids (250 +/- 37 to 1427 +/- 144 mumol/l) and free glycerol (98 +/- 27 to 232 +/- 41 mumol/l) within 48 h of feed restriction, and thereafter the concentrations levelled off. The pigs also showed a significant decrease in plasma levels of glucose (6.01 +/- 0.20 to 4.62 +/- 0.12 mmol/l) within 48 h of fasting, followed by repeated increase until the end of the experimental period. A significant decrease in plasma insulin-like growth factor I (84 +/- 13 to 65 +/- 7 ng/ml) was observed after 16 h, which continued during the whole period of feed withdrawal. However, no significant changes in plasma levels of adrenaline and noradrenaline during the period of increased lipolysis were detected. Therefore, the observed stimulation of lipolysis in growing swine during fasting is not the result of an increase in plasma concentration of catecholamines.