title: Mifepristone is a Vasodilator Due to the Inhibition of Smooth Muscle Cells L-Type Ca2+ Channels.
abstract: Derived from the estrane progestins, mifepristone was the first synthetic steroid of this class employed as abortifacient in the first months of pregnancy. Mifepristone reduces high potassium-induced contraction and prevents calcium-induced contraction. At the vascular level, mifepristone induces direct relaxation in rat and human arteries, and this effect seems to be endothelium- and NO independent, suggesting that the vascular smooth muscle is its target. Moreover, mifepristone's effect could involve the modulation of different calcium channels. The aim of the present study is to analyze the involvement of calcium channels in the relaxation induced by mifepristone on vascular smooth muscle cells (VSMCs). Planar cell surface area (PCSA) technique was used to analyze the effect of mifepristone on the VSMC contractility, and the whole cell configuration of patch-clamp technique to measure the activity of L-type Ca(2+) channels (LTCC) in A7r5 cells. Regarding the PCSA technique, mifepristone induced relaxation of the VSMC previously contracted by different agents. Also, a rapid inhibitory effect on basal and BAY K8644-stimulated calcium current was observed, which indicates that this drug has the ability to block LTCC. These results suggest that mifepristone induces relaxation on the VSMCs due to the inhibition of the calcium channels.
authors.affiliation: Centro de Investigação em Ciências da Saúde, University of Beira Interior, Covilhã, Portugal.
authors.forename: Melissa
authors.initials: M
authors.lastname: Mariana
authors.affiliation: Centro de Investigação em Ciências da Saúde, University of Beira Interior, Covilhã, Portugal.
authors.forename: Joana
authors.initials: J
authors.lastname: Feiteiro
authors.affiliation: Centro de Investigação em Ciências da Saúde, University of Beira Interior, Covilhã, Portugal ecairrao@fcsaude.ubi.pt.
authors.forename: Elisa
authors.initials: E
authors.lastname: Cairrao
authors.affiliation: Centro de Investigação em Ciências da Saúde, University of Beira Interior, Covilhã, Portugal.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Verde
mesh_terms: D000818:Animals; D020746:Calcium Channels, L-Type / Q000378:metabolism / Q000502:physiology*; D002460:Cell Line; D015735:Mifepristone / Q000008:administration & dosage*; D009126:Muscle Relaxation / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D009638:Norepinephrine / Q000008:administration & dosage; D051381:Rats; D012701:Serotonin / Q000008:administration & dosage; D014665:Vasodilator Agents / Q000008:administration & dosage*
chemical_list: D020746:Calcium Channels, L-Type; D014665:Vasodilator Agents; D015735:Mifepristone; D012701:Serotonin; D009638:Norepinephrine
keywords: A7r5 cells; calcium channels; mifepristone; relaxation