The lipolytic effect of beta 1- and beta 2-adrenoceptor activation in healthy human volunteers

1. We investigated the effect of activation beta 1- and beta 2-adrenoceptors on the process of lipolysis in human volunteers. Ten male subjects underwent a single-blind randomized cross-over trial using infusions of terbutaline (a specific beta 2-adrenoceptor agonist), xamoterol (a partial beta 1-agonist with beta 2-adrenoceptor blocking activity) and saline (placebo control). The effect of these infusions on plasma potassium, glucose, free fatty acids (FFA) (total and individual) and insulin levels was studied. 2. Terbutaline infusion induced a significant rise in plasma glucose and a fall in plasma potassium in keeping with its beta 2-adrenoceptor stimulant properties. Xamoterol infusion had no significant effect on these values. Terbutaline infusion caused a greater rise in total and individual FFA than xamoterol, but both effects were significantly different from placebo. 3. The possible reasons for these results and their implications on the beta-adrenergic control of lipolysis are discussed.