Abstract
The responses of plasma free fatty acid, glucose, lactate, insulin and growth hormone to intravenous administration of the predominantly β-2 stimulant, salbutamol, were studied in nine normal subjects. Four subjects received the predominantly β-1 blocking agent, practolol, together with salbutamol. Salbutamol produced a marked rise in free fatty acid levels and there was also an appreciable increase in insulin values; lactate levels rose moderately and glucose values increased slightly; growth hormone levels were not affected. Practolol did not alter the free fatty acid response; it diminished but did not appear to abolish the insulin response, and it appeared to suppress the lactate and glucose rises. Tentative proposals are made regarding the nature of the β-receptor subtypes responsible for mediating these effects; most definite is the suggestion that lipolysis is subserved by β-2 receptors. Possible clinical implications are briefly discussed.