[Effects of adrenergic blockade on adipose tissue lipolysis provoked in cats and humans by intravenous perfusion of isoprenaline]

Abstract

An intravenous infusion of isoprenaline (1 mug/kg/mn during 4 h) elicited a rise in serum free fatty acids (FFA) and glucose in anaesthetised cats. The effect reached a peak in 1 h and was then maintained at a plateau level for the remainder of the infusion. Acebutolol and practolol (0,1-10 mg/kg, p.o.) were more potent in reducing the concentration of free fatty acids (FFA) than in lowering glucose. Propranolol was roughly equipotent on FFA and glucose. In 6 fasted human volunteers, an intravenous infusion of isoprenaline (0,03 mug/kg/mn during 15 min) stimulated a rise in serum FFA. Peak values were attained rapidly and FFA levels began to fall soon after the end of the infusion. Blood glucose concentration was not changed. A placebo, given after the first infusion of isoprenaline, did not significantly affect the response to 2 further infusions at 2 and 4 h later. An oral dose of acebutolol (300 mg) largely suppressed the lipolytic effect of the 2nd and 3rd isoprenaline infusions, the degrees of inhibition being 70 p.cent and 85 p.cent respectively. The same dose of practolol was considerably less effective in inhibiting lipolysis (37 p.cent and 25 p.cent inhibition).