A trial for kinetic evaluation of the antagonistic potency of several beta-antagonists on presynaptic beta-adrenoceptors.
The antagonistic potency, pA2, of several non-selective beta-antagonists on presynaptic beta-adrenoceptors was evaluated using a parallel line assay and MacKay's equation against isoproterenol-induced increases in 3H release in isolated guinea-pig pulmonary arteries preloaded with 3H-norepinephrine. Cumulatively applied isoproterenol at 10(-9) M, 10(-8) M and 10(-7) M dose-dependently increased 3H release evoked by transmural field stimulation at 1 Hz. beta-Antagonists tested dose-dependently antagonized the isoproterenol-induced increases. The order of pA2 was carteolol (11.23 +/- 0.09) greater than nadolol (9.78 +/- 0.05) greater than pindolol (9.59 +/- 0.03) greater than propranolol (9.26 +/- 0.17). Carteolol has the highest pA2 and is a useful tool for clarifying whether or not presynaptic beta-adrenoceptors tonically function.
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D002354:Carteolol / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000037:antagonists & inhibitors; D007700:Kinetics; D008297:Male; D009248:Nadolol / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism; D010869:Pindolol / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D011651:Pulmonary Artery / Q000187:drug effects / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*
D000319:Adrenergic beta-Antagonists; D011943:Receptors, Adrenergic, beta; D009248:Nadolol; D002354:Carteolol; D011433:Propranolol; D010869:Pindolol; D007545:Isoproterenol; D009638:Norepinephrine