Endothelin-1 induces contraction of female rat internal pudendal and clitoral arteries through ET(A) receptor and rho-kinase activation.
BACKGROUND
Endothelin-1 (ET-1), a potent vasoconstrictor peptide, acts mainly through the Gprotein-coupled ET(A) receptor (ET(A)R). Increased vascular ET-1 production and constrictor sensitivity have been observed in various cardiovascular diseases, including hypertension, as well as erectile dysfunction. The internal pudendal artery (IPA) supplies blood to the vagina and clitoris. Inadequate blood flow through the IPA may lead to insufficient vaginal engorgement and clitoral tumescence.


OBJECTIVE
Characterize the effects of ET-1 on the IPA and clitoral artery (CA).


METHODS
IPA and CA from female Sprague Dawley rats (225-250 g) were mounted in myograph chambers. Arterial segments were submitted to increasing concentrations of ET-1 (10-10-10-6 M). Segments were incubated with the ET(A)R antagonist, atrasentan (10-8 M) or the Rho-kinase inhibitor, Y-27632 (10-6 M) 30 minutes prior to agonist exposure. All E(max) values are expressed as % KCl-induced maximal contraction. ET(A)R, RhoA, and Rho-kinase expression from IPA was evaluated by Western blot. mRNA of preproET-1, ET(A)R, ET(B)R, RhoA, and Rho-kinase were measured by real time PCR.


METHODS
ET-1 constrictor sensitivity in IPA and CA, protein expression and messenger RNA levels of ET-1-mediated constriction components.


RESULTS
ET-1 concentration-dependently contracted IPA (% Contraction and pD2, respectively: 156 ± 18, 8.2 ± 0.1) and CA (163 ± 12, 8.8 ± 0.08), while ET(A)R antagonism reduced ET-1-mediated contraction (IPA: 104 ± 23, 6.4 ± 0.2; CA: 112 ± 17, 6.6 ± 0.08). Pretreatment with Y-27632 significantly shifted ET-1 pD2 in IPA (108 ± 24, 7.9 ± 0.1) and CA (147 ± 58 and 8.0 ± 0.25). Protein expression of ET(A)R, ET(B)R, RhoA, and Rho-kinase were detected in IPA. IPA and CA contained preproET-1, ET(A)R, ET(B)R, RhoA, and Rho-kinase message.


CONCLUSIONS
We observed that the IPA and CA are sensitive to ET-1, signaling through the ET(A)R and Rho-kinase pathway. These data indicate that ET-1 may play a role in vaginal and clitoral blood flow and may be important in pathologies where ET-1 levels are elevated.
Allahdadi
Kyan J
KJ
Medical College of Georgia-Physiology, Augusta, GA, USA. Electronic address: kallahdadi@mcg.edu.
Hannan
Johanna L
JL
Medical College of Georgia-Physiology, Augusta, GA, USA.
Tostes
Rita C
RC
Medical College of Georgia-Physiology, Augusta, GA, USA; University of Sao Paulo-Pharmacology, Sao Paulo, Brazil.
Webb
R Clinton
RC
University of Sao Paulo-Pharmacology, Sao Paulo, Brazil.
D000818:Animals; D001158:Arteries / Q000502:physiology; D002987:Clitoris / Q000098:blood supply*; D019332:Endothelin-1 / Q000502:physiology; D005260:Female; D066298:In Vitro Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D044022:Receptor, Endothelin A / Q000502:physiology; D012039:Regional Blood Flow / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D014621:Vagina / Q000098:blood supply*; D014661:Vasoconstriction / Q000502:physiology*; D054460:rho-Associated Kinases / Q000502:physiology
D019332:Endothelin-1; D044022:Receptor, Endothelin A; D054460:rho-Associated Kinases
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