Antibronchospasmic, tachycardiac, and hypokalaemic effects of L-isoproterenol in guinea-pigs.
The relationship between antibronchospasmic, tachycardiac, or hypokalaemic effects and plasma concentration of L-isoproterenol (ISP) hydrochloride was investigated in guinea-pigs in vivo. ISP was infused at the rate of 10, 30, 50, 100, and 300 ng kg-1 min-1. The antibronchospasmic effect was expressed as the attenuation of methacholine-induced bronchospasm. The EC50 values of ISP for antibronchospasmic and tachycardiac effects were 5.12 nM and 3.95 nM, respectively. Although they were comparable to the values reported in vitro (7.23-0.358 nM, 1.77 nM), the concentration response relationship of ISP for antibronchospasmic effect was quite steep with a slope factor of more than six. Moreover, a decrease in plasma potassium level was not clearly detected. The experimental procedure in our present study was useful for evaluating antibronchospasmic and tachycardiac effects of beta-agonists.
Ohtani
H
H
Department of Pharmacy, University of Tokyo Hospital, Faculty of Medicine, Japan.
Yamamoto
K
K
Sawada
Y
Y
Iga
T
T
D000318:Adrenergic beta-Agonists / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D001986:Bronchial Spasm / Q000139:chemically induced / Q000188:drug therapy; D016085:Bronchoconstrictor Agents / Q000633:toxicity; D001993:Bronchodilator Agents / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D002316:Cardiotonic Agents / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D006339:Heart Rate / Q000187:drug effects; D007008:Hypokalemia / Q000139:chemically induced; D007262:Infusions, Intravenous; D007545:Isoproterenol / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D008297:Male; D016210:Methacholine Chloride / Q000633:toxicity; D011188:Potassium / Q000097:blood; D011312:Pressure; D012119:Respiration / Q000187:drug effects; D013237:Stereoisomerism; D013566:Sympathomimetics / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D013610:Tachycardia / Q000139:chemically induced
D000318:Adrenergic beta-Agonists; D016085:Bronchoconstrictor Agents; D001993:Bronchodilator Agents; D002316:Cardiotonic Agents; D013566:Sympathomimetics; D016210:Methacholine Chloride; D007545:Isoproterenol; D011188:Potassium