17beta-estradiol potentiates the cardiac cystic fibrosis transmembrane conductance regulator chloride current in guinea-pig ventricular myocytes.
There is a well-characterized membrane chloride current (ICl,cAMP) in the heart that can be activated by beta-adrenergic agonists and is due to expression of the cardiac isoform of the epithelial cystic fibrosis transmembrane conductance regulator (CFTR). We have investigated whether 17beta-estradiol (E2) modulates ICl,cAMP in single ventricular myocytes. Under whole-cell tight-seal voltage-clamp conditions, ICl,cAMP was evoked by exposing cells to 20 nM isoprenaline. On the addition of 30 microM E2, membrane slope conductance, measured at potentials near 0 mV, increased over that induced by isoprenaline alone by 2.46 +/- 0.16 (p < 0.001). The effects of E2 were concentration-dependent and described by a Hill Plot with an EC50 of 8.2 microM and a Hill coefficient of 1.63. The application of membrane-impermeant E2 conjugated to bovine serum albumin (E2-BSA) potentiated isoprenaline-evoked ICl,cAMP by approximately the same degree as that for the equivalent level of free E2. Cell surface binding was observed with confocal microscopy by using BSA-FITC tagged E2. This binding was inhibited by nonlabeled, nonconjugate E2, the specific E2 antagonist ICl 182,780, and incubation of E2coBSA with a specific anti-E2 antibody (E2885). ICl 182,780 (100 microM) significantly reduced the increase in ICl,cAMP evoked by 10 microM E2 to 1.46 +/- 0.10 (p < 0.02). The preincubation of myocytes with the NOS inhibitor N-omega-nitro-arginine (L-NNA, 1 mM) reduced the potentiation of ICl,cAMP by 30 microM E2, to 1.93 +/- 0.06 (p < 0.02), and for 10 microM E2, to 1.32 +/- 0.05 (p < 0.002). E2 also increased ICl,cAMP evoked by bath application of 0.5 microM Forskolin. These experiments demonstrate that, under our experimental conditions, E2 dramatically increases ICl,cAMP in ventricular myocytes by mechanisms involving a contribution by NOS, but that can be only partially accounted for through binding to classical plasma membrane estrogen receptor sites. This potentiation of ICl,cAMP by E2 may play a significant role in the observed clinical actions of E2 on the incidence of cardiac arrhythmias and hypertrophy.
Goodstadt
L
L
MRC Functional Genetics Unit, Parks Road, Oxford OX1 3QX, UK.
Powell
T
T
Figtree
G A
GA
D000818:Animals; D002316:Cardiotonic Agents / Q000494:pharmacology; D002395:Catecholamines / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000032:analysis / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000187:drug effects* / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology*; D004965:Estrogen Antagonists / Q000494:pharmacology; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology; D000077267:Fulvestrant; D006168:Guinea Pigs; D007545:Isoproterenol / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects* / Q000502:physiology; D032383:Myocytes, Cardiac / Q000737:chemistry / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000502:physiology; D019335:Nitroarginine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011485:Protein Binding / Q000502:physiology; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology; D011960:Receptors, Estrogen / Q000032:analysis / Q000502:physiology
D002316:Cardiotonic Agents; D002395:Catecholamines; D004965:Estrogen Antagonists; D011943:Receptors, Adrenergic, beta; D011960:Receptors, Estrogen; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin; D019335:Nitroarginine; D000077267:Fulvestrant; D004958:Estradiol; D000242:Cyclic AMP; D019001:Nitric Oxide Synthase; D007545:Isoproterenol