THE ROLE OF o^-ADRENOCEPTORS IN ADRENALINE- INDUCED HYPERKALAEMIA

The hyperkalaemic action of adrenaline was investigated in 44 anaesthetized domestic pigs. Plasma and epicardial concentrations of K were measured, in the latter case with an ion-selective electrode. Adrenaline 10 pgkg~ caused a rapid increase in the plasma concentration of K from 4.2 to 5.9 mmol litre'. The magnitude and the time course of epicardial concentration of K were similar. Alpha-adrenoceptor block with either phentolamine 5mgkg' (non-selective block) or prazosin 0.1 mg kg(selective cx,adrenoceptor block) abolished the hyperkalaemic effect of adrenaline in the plasma and on the epicardium. The a,-adrenoceptor agonist phenylephrine increased the K concentration, but the <x2-adrenoceptor agonist UK 14.304 did not cause any change in concentration. These results suggest that the hyperka/aemia induced by adrenaline occurs in the interstitial fluid of the myocardium and is mediated by <xradrenoceptors. These findings may be important in patients at risk of hyperka/aemia, with implications, for example, in the use ofsuxamethonium during induction of anaesthesia.