Direct action of estradiol-17 beta on the atrial action potential

The effect of the two C-17 isomers of estradiol on the shape of the action potential of rat atrial tissue was studied by means of classical glass electrodes for different concentrations of estradiol. Resting potential and upstroke were not affected by estradiol, but the duration of the action potential was reduced. Only estradiol-17 beta exhibits an effect in a concentration dependent way, while estradiol-17 alpha has no effect at all. The ionic mechanism was studied by adding specific ionic blockers to the perfusate. Since the effect was much less pronounced when a slow inward current blocker was added, it was concluded that estradiol-17 beta acts mainly via the slow inward current channel. Only a small part of the interaction takes place via the potassium outward channel.