title: Electrophysiologic effects of 17β-estradiol on pacemaker cells in sinoatrial nodes of rabbits.
abstract: To investigate the electrophysiological effects of 17β-estradiol on pacemaker cells in sinoatrial (SA) nodes of rabbits and the underlying mechanism, intracellular microelectrode technique was used to record action potential (AP) in SA node cells of rabbits. The results showed that: (1) 17β-estradiol (1, 10, 100 μmol/L) not only significantly decreased the amplitude of action potential (APA) and the maximal rate of depolarization (V(max)), but also decreased the velocity of diastolic (phase 4) depolarization (VDD) and rate of pacemaker firing (RPF) in a concentration-dependent manner. The AP duration at 50% repolarization (APD(50)) and at 90% repolarization (APD(90)) were prolonged. But the maximal diastolic potential (MDP) was not affected. (2) Pretreatment with tamoxifen (10 μmol/L), an inhibitor of estrogen receptor, did not block the electrophysiological effects of 17β-estradiol (10 μmol/L) on SA node cells. (3) Pretreatment with N(G)-nitro-L-arginine methyl ester (L-NAME, 100 μmol/L), a nitric oxide (NO) synthase inhibitor, completely abolished the electrophysiological effects of 17β-estradiol (10 μmol/L) on SA node cells. The results suggest that 17β-estradiol inhibits the electrophysiological activity of pacemaker cells in SA nodes of rabbits in a concentration-dependent manner possibly through a non-genomic mechanism related with NO.
authors.affiliation: Department of Physiology, Hebei Medical University, Shijiazhuang 050017, China.
authors.forename: Li-Bin
authors.initials: LB
authors.lastname: Zhou
authors.forename: Li-Lin
authors.initials: LL
authors.lastname: Song
authors.forename: Yue
authors.initials: Y
authors.lastname: Guan
authors.forename: Shu-Mei
authors.initials: SM
authors.lastname: Guo
authors.forename: Fang
authors.initials: F
authors.lastname: Yuan
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000200:Action Potentials; D000818:Animals; D055724:Electrophysiological Phenomena; D004958:Estradiol / Q000494:pharmacology*; D032383:Myocytes, Cardiac / Q000187:drug effects*; D011817:Rabbits; D012849:Sinoatrial Node / Q000166:cytology*
chemical_list: D004958:Estradiol