Metabolic and cardiovascular effects of isoprenaline and salbutamol in the dog.

1 The intravenous infusion of isoprenaline and salbutamol into the greyhound increased heart rate and levels of free fatty acids, lactic acid and glucose. 2 On terminating the infusions of isoprenaline the changes produced declined rapidly but the effects produced by salbutamol were more persistent. When high doses of salbutamol had been infused, glucose and lactic acid levels in fact increased during the 20 min following the infusions. 3 These results support suggestions that, in the dog, lipolysis is mediated by beta1-adrenoceptors and liver glycogenolysis by beta2-adrenoceptors. The beta-adrenoceptors mediating muscle glycogenolysis could not be assigned inequivocally to either subtype. 4 The differences in the behaviour of isoprenaline and salbutamol in the period following the infusions are considered to be due partly to slower removal of salbutamol. Increases in lactic acid levels after infusion of large amounts of salbutamol may be secondary to the persistence of high glucose levels.