Role of alpha-adrenoceptors in control of plasma potassium in conscious rabbits.

1. In conscious fed rabbits the intravenous infusion of amidephrine (10 micrograms kg-1 min-1), an alpha 1-adrenoceptor agonist, caused a significant increase in plasma potassium levels that was blunted by prazosin (50 micrograms kg-1, s.c.). Idazoxan failed to modify this response. 2. Clonidine (2 micrograms kg-1 min-1, i.v.), an alpha 2-adrenoceptor agonist, also evoked a hyperkalaemic response which was antagonized by idazoxan (1 microgram kg-1, s.c.), yohimbine (0.45 mg kg-1, s.c.) and prazosin (50 micrograms kg-1, s.c.). Apamin (40 micrograms kg-1, i.v. bolus) also suppressed the clonidine-mediated hyperkalaemia. 3. Verapamil (5 micrograms kg-1, s.c.) prevented both alpha 1- and alpha 2-adrenoceptor-mediated increase in plasma potassium levels. 4. It is concluded that in conscious fed rabbits both alpha 1- and alpha 2-adrenoceptor stimulation induce hyperkalaemia by activation of hepatic Ca(2+)-activated K(+)-channels.