Opposite effects of beta-adrenoceptor stimulation and 8-bromo-cyclic AMP on potassium efflux in mammalian heart muscle.
beta-adrenoceptor stimulation by isoprenaline increases the potassium efflux in beating guinea-pig atria. This effect is not mimicked by 8-bromo-cyclic AMP, a cyclic AMP analogue which exerts a positive inotropic effect in this preparation.