Apparent equilibrium constant between beta-adrenoceptors and a competitive antagonist on a cultured pacemaker cell of mammalian heart.

Heart cells from newborn rats and kittens were cultured. In both species the rate of pacemaker activity of single, cultured cells was increased by low concentrations of catecholamines. Tthe beta-adrenoceptor blocker (minus)-KL255 antagonized competitively the effects of both, (minus)-noradrenaline and (minus)-isoprenaline. A mean equilibrium constant of 3.6 times 10-10M between (minus)-KL255 and beta-adrenoceptors of single cells was estimated.