The Effects of β-Adrenergic Blockade on Body Composition in Free-Fed and Diet-Restricted rats

The effects of the non-selective β-adrenergic blocking agent propranolol (known for its anti-lipolytic activity) on body composition were investigated in growing male rats on normal unrestricted diet (N=7) and on diet restriction (N=7, 95% of controls). Three animals in each group were injected i.p. with 30 mg propranolol per kg body weight (bw) dissolved in saline, 5 days/week. This dose attenuates exercising heart rate by 25% and exercise training-induced enzyme activity. The remaining animals received saline. Fat, glycogen, moisture and non-ether extractable residue were determined in the homogenized residue of the whole animal. After 9 weeks on the experimental regimen, bw gain was significantly lower in the diet restricted rats, whereas propranolol had no effect on the bw gain. The percentage of fat, moisture and non-ether extractable residue were unchanged by either propranolol or diet restriction. However, glycogen content was significantly lower in the β-blocked rats either with or without diet restriciton. These data indicated that neither β-adrenergic blockade nor minimal diet restriction influences the percentage body fat, whereas body glycogen content is decreased under both conditions.