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.
Reverte
M
M
Department of Pharmacology, School of Medicine, University of Salamanca, Spain.
García-Barrado
M J
MJ
Moratinos
J
J
D000818:Animals; D001030:Apamin / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D003000:Clonidine / Q000008:administration & dosage / Q000494:pharmacology; D004146:Dioxanes / Q000494:pharmacology; D004983:Ethanolamines / Q000008:administration & dosage / Q000494:pharmacology; D006947:Hyperkalemia / Q000139:chemically induced; D019329:Idazoxan; D011188:Potassium / Q000097:blood*; D011224:Prazosin / Q000494:pharmacology; D011817:Rabbits; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D014700:Verapamil / Q000008:administration & dosage / Q000494:pharmacology
D015220:Calcium Channels; D004146:Dioxanes; D004983:Ethanolamines; D011942:Receptors, Adrenergic, alpha; D001030:Apamin; C016980:amidephrine; D014700:Verapamil; D003000:Clonidine; D011188:Potassium; D011224:Prazosin; D019329:Idazoxan