GPER regulates endothelin-dependent vascular tone and intracellular calcium.
OBJECTIVE
An increase in intracellular vascular smooth muscle cell calcium concentration (VSMC [Ca(2+)](i)) is essential for endothelin-1 (ET-1)-induced vasoconstriction. Based on previous findings that activation of the G protein-coupled estrogen receptor (GPER) inhibits vasoconstriction in response to ET-1 and regulates [Ca(2+)](i) in cultured VSMC, we investigated whether endogenous GPER regulates ET-1-induced changes in VSMC [Ca(2+)](i) and constriction of intact arteries.


METHODS
Pressurized carotid arteries of GPER-deficient (GPER(0)) and wildtype (WT) mice were loaded with the calcium indicator fura 2-AM. Arteries were stimulated with the GPER-selective agonist G-1 or solvent followed by exposure to ET-1. Changes in arterial diameter and VSMC [Ca(2+)](i) were recorded simultaneously. Vascular gene expression levels of ET(A) and ET(B) receptors were determined by qPCR.


RESULTS
ET-1-dependent vasoconstriction was increased in arteries from GPER(0) compared to arteries from WT mice. Despite the more potent vasoconstriction to ET-1, GPER deficiency was associated with a marked reduction in the ET-1-stimulated VSMC [Ca(2+)](i) increase, suggesting an increase in myofilament force sensitivity to [Ca(2+)](i). Activation of GPER by G-1 had no effect on vasoconstriction or VSMC [Ca(2+)](i) responses to ET-1, and expression levels of ET(A) or ET(B) receptor were unaffected by GPER deficiency.


CONCLUSIONS
These results demonstrate that endogenous GPER inhibits ET-1-induced vasoconstriction, an effect that may be associated with reduced VSMC Ca(2+) sensitivity. This represents a potential mechanism through which GPER could contribute to protective effects of endogenous estrogen in the cardiovascular system.
Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, United States.
Matthias R
MR
Meyer
Angela S
AS
Field
Nancy L
NL
Kanagy
Matthias
M
Barton
Eric R
ER
Prossnitz
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002339:Carotid Arteries / Q000378:metabolism; D019332:Endothelin-1 / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000737:chemistry; D016257:Fura-2 / Q000031:analogs & derivatives / Q000737:chemistry; D005786:Gene Expression Regulation; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D044022:Receptor, Endothelin A / Q000235:genetics; D044023:Receptor, Endothelin B / Q000235:genetics; D011960:Receptors, Estrogen; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D014661:Vasoconstriction
D019332:Endothelin-1; D005456:Fluorescent Dyes; C532507:GPER1 protein, mouse; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D011960:Receptors, Estrogen; D043562:Receptors, G-Protein-Coupled; C049925:fura-2-am; D002118:Calcium; D016257:Fura-2