Weight loss induced by chronic phenylpropanolamine: anorexia and brown adipose tissue thermogenesis.

The effects of chronic treatment with phenylpropanolamine (PPA) on body weight (BW), food intake (FI), and water intake (WI) and interscapular brown adipose tissue (IBAT) thermogenesis in adult male Sprague-Dawley rats were evaluated in 2 experiments. In Experiment 1, rats were treated (IP) twice daily (0900 and 2100 hr) for 12 days with either saline or 5, 10, or 20 mg/kg dl-PPA. Rats treated with 20 mg/kg dl-PPA exhibited significant decreases in both FI and BW but not WI. Basal IBAT temperature was slightly increased in chronic 20 mg/kg dl-PPA rats and there was no evidence of tolerance to the acute IBAT thermogenic effect of 20 mg/kg dl-PPA. In Experiment 2, rats were treated twice daily (0900 and 2100 hr) for 12 days with either saline or 20 mg/kg of either d-PPA or l-PPA. There was a 2-fold difference in the potency of these PPA isomers on FI, BW and IBAT thermogenesis. Body composition analyses revealed that l-PPA, but not d-PPA, induced a significant loss of carcass lipid without significant changes in carcass ash, water or protein levels. These data suggest that the weight-reducing action of PPA may reflect a combined effect of this drug on both food intake and BAT thermogenesis.