Antiarrhythmic effect and its underlying ionic mechanism of 17beta-estradiol in cardiac myocytes.
1. The effects of oestrogens on action potential and membrane currents were examined in single guinea-pig atrial myocytes. 2. 17Beta-estradiol (3-10 microM) shortened the action potential duration without significant changes in the resting membrane potential. E-4031 (1 microM) markedly prolonged the action potential duration and induced early afterdepolarization, and 17beta-estradiol (10 microM) abolished it. 3. When cells were perfused in isoproterenol-containing solution, action potentials due to abnormal automaticity caused by membrane depolarization developed, and were also inhibited by 17beta-estradiol. 4. Under voltage clamp conditions, the voltage-dependent Ca2+ currents consisted of both T-(I(Ca,T)) and L-type (I(Ca,L)). 17Beta-estradiol reduced I(Ca,L) concentration-dependently, while it (10 microM) suppressed I(Ca,T) only by approximately 10%. 17Beta-estradiol did not affect time courses of I(Ca,L) inactivation, but it shifted the steady-state inactivation curve to more negative potentials. 5. 17Beta-estradiol (10 microM) did not affect the time-dependent K+ current (I(K)), referred to as I(Kr) and I(Ks) and inwardly rectifying K+ current. However, 17beta-estradiol (30 microM) or diethylstilbestrol (10 microM) inhibited K+ currents. 6. DES and ethinylestradiol (EES) also suppressed I(Ca,L), but testosterone and progesterone failed to inhibit I(Ca,L) The potency of the inhibitory effect on I(Ca,L) was DES> EES> 17beta-estradiol. 7. 17Beta-estradiol and DES also inhibited the cyclic AMP-enhanced I(Ca,L), but cyclic GMP in the pipette or pretreatment of L-NAME could not block the effects of oestrogen on I(Ca,L). 8 These results suggest that oestrogen specifically has antiarrhythmic effects, possibly by acting the L-type Ca2+ channels. The antiarrhythmic effects of oestrogens may contribute to the cardioprotective actions of oestrogens.
Nakajima
T
T
The 2nd Department of Internal Medicine, University of Tokyo, Japan.
Iwasawa
K
K
Oonuma
H
H
Morita
T
T
Goto
A
A
Wang
Y
Y
Hazama
H
H
D000200:Action Potentials / Q000187:drug effects; D000728:Androgens / Q000494:pharmacology; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects; D020746:Calcium Channels, L-Type; D002316:Cardiotonic Agents / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology*; D004965:Estrogen Antagonists / Q000494:pharmacology; D004968:Estrogens, Non-Steroidal / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009206:Myocardium / Q000166:cytology*; D018408:Patch-Clamp Techniques; D010880:Piperidines / Q000494:pharmacology; D026902:Potassium Channel Blockers; D011725:Pyridines / Q000494:pharmacology
D000728:Androgens; D000889:Anti-Arrhythmia Agents; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D002316:Cardiotonic Agents; D004965:Estrogen Antagonists; D004968:Estrogens, Non-Steroidal; D010880:Piperidines; D026902:Potassium Channel Blockers; D011725:Pyridines; C063968:E 4031; D004958:Estradiol; D007545:Isoproterenol