Acute effects of exercise on triacylglycerol metabolism in fasted, untrained rats treated with nadolol.

The current study investigated the early response of some determinants of triacylglycerol (TG) metabolism to acute exercise in rats that were treated or not with the nonselective beta-adrenergic blocker, nadolol (25 mg.kg b.wt.-1.day-1 for 30 days). Measurements of hepatic TG secretion rate (HTGSR), postheparin plasma hepatic TG lipase (HTGL) activity, and that of lipoprotein lipase (LPL) in postheparin plasma, heart, vastus lateralis muscle (VLM), white (WAT) and brown (BAT) adipose tissues were carried out in untrained rats at rest or immediately after a 1 h run on treadmill (22 m.min-1, 0 degrees grade). All animals were in the fasted state. Exercise reduced serum TG levels (46% below resting levels) and doubled those of nonesterified fatty acids. HTGSR was enhanced (+28%) by exercise while HTGL activity was not modified. The decrease in postheparin plasma LPL activity (-24%) caused by exercise was consistent with a reduction in enzyme activity in WAT (-32%), BAT (-45%) and heart (-25%). One h of treadmill running did not influence LPL activity in VLM. beta-Adrenergic blockade did not affect any of the variables of lipid metabolism, except for a slight decrease in specific activity of LPL in the heart (-14%). This study demonstrates that absolute variations in HTGSR and in LPL activity cannot account for the acute fall in serum TG levels caused by moderate exercise, in fasted, untrained rats. In addition, these results show that the beta-adrenergic pathway is either not involved in, or not necessary for, the latter effects of exercise on TG metabolism.