title: Relaxin deficiency attenuates pregnancy-induced adaptation of the mesenteric artery to angiotensin II in mice.
abstract: Pregnancy is associated with reduced peripheral vascular resistance, underpinned by changes in endothelial and smooth muscle function. Failure of the maternal vasculature to adapt correctly leads to serious pregnancy complications, such as preeclampsia. The peptide hormone relaxin regulates the maternal renal vasculature during pregnancy; however, little is known about its effects in other vascular beds. This study tested the hypothesis that functional adaptation of the mesenteric and uterine arteries during pregnancy will be compromised in relaxin-deficient (Rln(-/-)) mice. Smooth muscle and endothelial reactivity were examined in small mesenteric and uterine arteries of nonpregnant (estrus) and late-pregnant (day 17.5) wild-type (Rln(+/+)) and Rln(-/-) mice using wire myography. Pregnancy per se was associated with significant reductions in contraction to phenylephrine, endothelin-1, and ANG II in small mesenteric arteries, while sensitivity to endothelin-1 was reduced in uterine arteries of Rln(+/+) mice. The normal pregnancy-associated attenuation of ANG II-mediated vasoconstriction in mesenteric arteries did not occur in Rln(-/-) mice. This adaptive failure was endothelium-independent and did not result from altered expression of ANG II receptors or regulator of G protein signaling 5 (Rgs5) or increases in reactive oxygen species generation. Inhibition of nitric oxide synthase with l-NAME enhanced ANG II-mediated contraction in mesenteric arteries of both genotypes, whereas blockade of prostanoid production with indomethacin only increased ANG II-induced contraction in arteries of pregnant Rln(+/+) mice. In conclusion, relaxin deficiency prevents the normal pregnancy-induced attenuation of ANG II-mediated vasoconstriction in small mesenteric arteries. This is associated with reduced smooth muscle-derived vasodilator prostanoids.
authors.affiliation: School of BioSciences, The University of Melbourne, Parkville, Victoria, Australia;
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Marshall
authors.affiliation: School of BioSciences, The University of Melbourne, Parkville, Victoria, Australia;
authors.forename: Chen Huei
authors.initials: CH
authors.lastname: Leo
authors.affiliation: School of BioSciences, The University of Melbourne, Parkville, Victoria, Australia;
authors.forename: Sevvandi N
authors.initials: SN
authors.lastname: Senadheera
authors.affiliation: Gynaecology Research Centre, Department of Obstetrics and Gynaecology, The University of Melbourne and Royal Women's Hospital, Parkville, Victoria, Australia; and.
authors.forename: Jane E
authors.initials: JE
authors.lastname: Girling
authors.affiliation: Department of Physiology, Monash University, Victoria, Australia; and School of Rural Health, Monash University, Victoria, Australia.
authors.forename: Marianne
authors.initials: M
authors.lastname: Tare
authors.affiliation: School of BioSciences, The University of Melbourne, Parkville, Victoria, Australia; ljparry@unimelb.edu.au.
authors.forename: Laura J
authors.identifier: 0000-0002-6883-3418
authors.initials: LJ
authors.lastname: Parry
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000804:Angiotensin II / Q000378:metabolism*; D000818:Animals; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology; D008638:Mesenteric Arteries / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology; D011945:Receptors, Angiotensin / Q000502:physiology; D012065:Relaxin / Q000235:genetics / Q000378:metabolism*; D055988:Uterine Artery / Q000502:physiology; D014664:Vasodilation / Q000502:physiology
chemical_list: D011945:Receptors, Angiotensin; D000804:Angiotensin II; D012065:Relaxin
keywords: angiotensin; pregnancy; relaxin; vascular