title: Non-genomic vasorelaxant effects of 17β-estradiol and progesterone in rat aorta are mediated by L-type Ca2+ current inhibition.
abstract: OBJECTIVE
  The sex hormones 17β-estradiol (βES) and progesterone (PRG) induce rapid non-genomic vasodilator effects which could be protective for the cardiovascular system. The purpose of this study was to analyze the mechanisms underlying their vasodilator effect in rat aortic smooth muscle preparations.
  
  
  METHODS
  Endothelium-denuded aorta artery rings were prepared from male Wistar rats and incubated in an organ bath. The contractions of the preparation were recorded through isometric transducers. The effects of the hormones on K(+) current and L-type Ca(2+) current (LTCC) were analyzed by using the whole cell voltage-clamp technique in A7r5 cells.
  
  
  RESULTS
  Both βES and PRG (1-100 μmol/L) concentration-dependently relaxed the endothelium-denuded aortic rings contracted by (-)-Bay K8644 (0.1 μmol/L) or by KCl (60 mmol/L). The IC(50) values of the two hormones were not statistically different. The K(V) channel blocker 4-aminopyridine (2 mmol/L), BK(Ca) channel blocker tetraethylammonium (1 mmol/L) and K(ATP) channel blocker glibenclamide (10 μmol/L) did not significantly modify the relaxant effect of the hormones. On the other hand, the blockage of the intracellular βES and PRG receptors with estradiol receptor antagonists ICI 182,780 (1 μmol/L) and PRG receptor antagonist mifepristone (30 μmol/L), respectively, did not significantly modify the relaxant action of the hormones. In A7r5 cells, both the hormones (1-100 μmol/L) rapidly and reversibly inhibited the basal and BAY-stimulated LTCC. However, these hormones had no effect on the basal K(+) current.
  
  
  CONCLUSIONS
  The vasorelaxant effects of βES and PRG are due to the inhibition of LTCC. The K(+) channels are not involved in the effects.
authors.affiliation: Centro de Investigação em Ciências da Saúde, Universidade da Beira Interior, Covilhã, Portugal. ecairrao@fcsaude.ubi.pt
authors.forename: Elisa
authors.initials: E
authors.lastname: Cairrão
authors.forename: Ezequiel
authors.initials: E
authors.lastname: Alvarez
authors.forename: João Miguel
authors.initials: JM
authors.lastname: Carvas
authors.forename: Antonio Jose
authors.initials: AJ
authors.lastname: Santos-Silva
authors.forename: Ignacio
authors.initials: I
authors.lastname: Verde
mesh_terms: D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000187:drug effects* / Q000378:metabolism; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000494:pharmacology*; D047629:Estrogen Receptor beta / Q000187:drug effects / Q000378:metabolism; D006727:Hormone Antagonists / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D011980:Receptors, Progesterone / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D047629:Estrogen Receptor beta; D006727:Hormone Antagonists; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D011980:Receptors, Progesterone; D014665:Vasodilator Agents; D011374:Progesterone; D004958:Estradiol