Carteolol is a weak partial agonist on beta 3-adrenergic receptors in brown adipocytes.
The ability of the beta 1/beta 2 partial agonist carteolol to act as an agonist on beta 3-adrenergic receptors was investigated by studying its ability to stimulate thermogenesis (oxygen consumption) in brown fat cells isolated from hamsters. Carteolol was able to induce thermogenesis, with an EC50 of 5 microM, but it was only a partial (40%) agonist. D,L-Propranolol had a pKB of 5.1 as an antagonist against carteolol in this system, indicating that the carteolol effect was probably mediated via beta 3-receptors. Also in mouse and rat cells, carteolol was a partial agonist with EC50 values around 1 microM. Being a partial agonist, carteolol acted as an antagonist against norepinephrine-, BRL-37344-, or CGP-12177-stimulated thermogenesis with a pKB of approximately 5. The partial agonist effects of carteolol are discussed in relation to the absence of agonist effect of this compound on guinea-pig taenia cecum beta 3-receptors and in relation to the possible plurality of beta 3-receptors.
Zhao
J
J
Wenner-Gren Institute, Arrhenius Laboratories F3, Stockholm University, Sweden.
Cannon
B
B
Nedergaard
J
J
D002001:Adipose Tissue, Brown / Q000187:drug effects* / Q000378:metabolism; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D002354:Carteolol / Q000494:pharmacology*; D006224:Cricetinae; D005260:Female; D008297:Male; D008647:Mesocricetus; D051379:Mice; D010101:Oxygen Consumption / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*; D022702:Receptors, Adrenergic, beta-3
D000318:Adrenergic beta-Agonists; D011943:Receptors, Adrenergic, beta; D022702:Receptors, Adrenergic, beta-3; D002354:Carteolol