Estrogen regulates {beta}1-subunit expression in Ca(2+)-activated K(+) channels in arteries from reproductive tissues.
Daily estradiol-17beta (E(2)beta) increases basal uterine blood flow (UBF) and enhances acute E(2)beta-mediated increases in UBF in ovariectomized nonpregnant ewes. The acute E(2)beta-mediated rise in UBF involves vascular smooth muscle (VSM) large-conductance Ca(2+)-activated K(+) channels (BK(Ca)). BK(Ca) consist of pore-forming alpha-subunits and regulatory beta(1)-subunits that modulate channel function and E(2)beta responsiveness. It is unclear whether E(2)beta also alters subunit expression and thus channel density and/or function, thereby contributing to the rise in basal UBF and enhanced UBF responses that follow daily E(2)beta. Therefore, we examined BK(Ca) subunit expression by using reverse transcription-PCR and immunoblot analysis of arterial VSM from reproductive and nonreproductive tissues and myometrium from ovariectomized nonpregnant ewes after daily E(2)beta (1 microg/kg iv) or vehicle without or with acute E(2)beta (1 microg/kg). Tissue distribution was determined by immunohistochemistry. Acute E(2)beta did not alter alpha- or beta(1)-subunit expression in any tissue (P > 0.1). Daily E(2)beta also did not affect alpha-subunit mRNA or protein in any tissue (P > 0.1) or mesenteric arterial VSM beta(1)-subunit. However, daily E(2)beta increased uterine and mammary arterial VSM beta(1)-subunit mRNA by 32% and 83% (P < 0.05), uterine VSM protein by 30%, and myometrial beta(1)-subunit mRNA and protein by 74% (P < or = 0.005). Immunostaining of uterine arteries, myometrium, and intramyometrial arteries paralleled immunoblot analyses for both subunits. Although BK(Ca) density is unaffected by daily and acute E(2)beta, daily E(2)beta increases beta(1)-subunit in proximal and distal uterine arterial VSM. Thus prolonged E(2)beta exposure may alter BK(Ca) function, estrogen responsiveness, and basal vascular tone and reactivity in reproductive arteries by modifying alpha:beta(1) stoichiometry.
Nagar
Deepa
D
Department of Pediatrics, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd., Dallas, TX 75390-9063, USA.
Liu
Xiao-Tie
XT
Rosenfeld
Charles R
CR
D000818:Animals; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D007150:Immunohistochemistry; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008323:Mammary Arteries / Q000187:drug effects* / Q000502:physiology*; D008638:Mesenteric Arteries / Q000187:drug effects / Q000502:physiology; D009215:Myometrium / Q000098:blood supply*; D024681:Potassium Channels, Calcium-Activated / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012756:Sheep; D014661:Vasoconstriction / Q000502:physiology
D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D021122:Protein Subunits; D004958:Estradiol