title: Effect of transverse aortic constriction on cardiac structure, function and gene expression in pregnant rats.
abstract: BACKGROUND
  There is an increased risk of heart failure and pulmonary edema in pregnancies complicated by hypertensive disorders. However, in a previous study we found that pregnancy protects against fibrosis and preserves angiogenesis in a rat model of angiotensin II induced cardiac hypertrophy. In this study we test the hypothesis that pregnancy protects against negative effects of increased afterload.
  
  
  METHODS
  Pregnant (gestational day 5.5-8.5) and non-pregnant Wistar rats were randomized to transverse aortic constriction (TAC) or sham surgery. After 14.2 ± 0.14 days echocardiography was performed. Aortic blood pressure and left ventricular (LV) pressure-volume loops were obtained using a conductance catheter. LV collagen content and cardiomyocyte circumference were measured. Myocardial gene expression was assessed by real-time polymerase chain reaction.
  
  
  RESULTS
  Heart weight was increased by TAC (p<0.001) but not by pregnancy. Cardiac myocyte circumference was larger in pregnant compared to non-pregnant rats independent of TAC (p = 0.01), however TAC per se did not affect this parameter. Collagen content in LV myocardium was not affected by pregnancy or TAC. TAC increased stroke work more in pregnant rats (34.1 ± 2.4 vs 17.5 ± 2.4 mmHg/mL, p<0.001) than in non-pregnant (28.2 ± 1.7 vs 20.9 ± 1.5 mmHg/mL, p = 0.06). However, it did not lead to overt heart failure in any group. In pregnant rats, α-MHC gene expression was reduced by TAC. Increased in the expression of β-MHC gene was higher in pregnant (5-fold) compared to non-pregnant rats (2-fold) after TAC (p = 0.001). Nine out of the 19 genes related to cardiac remodeling were affected by pregnancy independent of TAC.
  
  
  CONCLUSIONS
  This study did not support the hypothesis that pregnancy is cardioprotective against the negative effects of increased afterload. Some differences in cardiac structure, function and gene expression between pregnant and non-pregnant rats following TAC indicated that afterload increase is less tolerated in pregnancy.
authors.affiliation: Women's Health and Perinatology Research Group, Department of Clinical Medicine, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway ; Department of Pediatrics, University Hospital of Northern Norway, Tromsø, Norway.
authors.forename: Nils Thomas
authors.initials: NT
authors.lastname: Songstad
authors.affiliation: Cardiovascular Research Group, Department of Medical Biology, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway.
authors.forename: David
authors.initials: D
authors.lastname: Johansen
authors.affiliation: Cardiovascular Research Group, Department of Medical Biology, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway.
authors.forename: Ole-Jacob
authors.initials: OJ
authors.lastname: How
authors.affiliation: Department of Pediatrics, University Hospital of Northern Norway, Tromsø, Norway ; Pediatric Research Group, Department of Clinical Medicine, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway.
authors.forename: Per Ivar
authors.initials: PI
authors.lastname: Kaaresen
authors.affiliation: Cardiovascular Research Group, Department of Medical Biology, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway.
authors.forename: Kirsti
authors.initials: K
authors.lastname: Ytrehus
authors.affiliation: Women's Health and Perinatology Research Group, Department of Clinical Medicine, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway ; Department of Obstetrics and Gynecology, University Hospital of Northern Norway, Tromsø, Norway.
authors.forename: Ganesh
authors.initials: G
authors.lastname: Acharya
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000254:growth & development / Q000378:metabolism* / Q000473:pathology*; D006332:Cardiomegaly / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D002478:Cells, Cultured; D003251:Constriction, Pathologic / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D004452:Echocardiography; D005260:Female; D005355:Fibrosis / Q000378:metabolism / Q000473:pathology*; D015870:Gene Expression; D006321:Heart / Q000503:physiopathology*; D007124:Immunoenzyme Techniques; D009389:Neovascularization, Pathologic / Q000378:metabolism / Q000473:pathology*; D011247:Pregnancy; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D012333:RNA, Messenger