title: Newborn lamb coronary artery reactivity is programmed by early gestation dexamethasone before the onset of systemic hypertension.
abstract: Exposure of the early gestation ovine fetus to exogenous glucocorticoids induces organ-specific alterations in postnatal cardiovascular physiology. To determine whether early gestation corticosteroid exposure alters coronary reactivity before the development of systemic hypertension, dexamethasone (0.28 mg x kg(-1) x day(-1)) was administered to pregnant ewes by intravenous infusion over 48 h beginning at 27 days gestation (term, 145 days). Vascular responsiveness was assessed in endothelium-intact coronary arteries isolated from 1-wk-old steroid-exposed and age-matched control lambs (N = 6). Calcium imaging was performed in fura 2-loaded primary cultures of vascular smooth muscle cells (VSMC) from the harvested coronary arteries. Early gestation steroid exposure did not significantly alter mean arterial blood pressure or coronary reactivity to KCl, thromboxane A(2) mimetic U-46619, or ANG II. Steroid exposure significantly increased coronary artery vasoconstriction to acetylcholine and endothelin-1. Vasodilatation to adenosine, but not nitroprusside or forskolin, was significantly attenuated following early gestation steroid exposure. Endothelin-1 or U-46619 stimulation resulted in a comparable increase in intracellular calcium concentration ([Ca(2+)](i)) in coronary VSMC isolated from either dexamethasone-treated or control animals. However, the ANG II- or KCl-mediated increase in [Ca(2+)](i) in control VSMC was significantly attenuated in VSMC harvested from dexamethasone-treated lambs. Coronary expression of muscle voltage-gated l-type calcium channel alpha-1 subunit protein was not significantly altered by steroid exposure, whereas endothelial nitric oxide synthase expression was attenuated. These findings demonstrate that early gestation glucocorticoid exposure elicits primary alterations in coronary responsiveness before the development of systemic hypertension. Glucocorticoid-induced alterations in coronary physiology may provide a mechanistic link between an adverse intrauterine environment and later cardiovascular disease.
authors.affiliation: Division of Neonatology, Department of Pediatrics, Children's Hospital of Iowa, Iowa City, IA 52242, USA. robert-roghair@uiowa.edu
authors.forename: Robert D
authors.initials: RD
authors.lastname: Roghair
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Segar
authors.forename: Ram V
authors.initials: RV
authors.lastname: Sharma
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Zimmerman
authors.forename: D K
authors.initials: DK
authors.lastname: Jagadeesha
authors.forename: Emily M
authors.initials: EM
authors.lastname: Segar
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Scholz
authors.forename: Fred S
authors.initials: FS
authors.lastname: Lamb
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D003331:Coronary Vessels / Q000187:drug effects / Q000196:embryology* / Q000503:physiopathology*; D003907:Dexamethasone / Q000008:administration & dosage* / Q000009:adverse effects*; D004198:Disease Susceptibility / Q000139:chemically induced / Q000196:embryology / Q000503:physiopathology; D005260:Female; D005865:Gestational Age; D006973:Hypertension / Q000139:chemically induced* / Q000151:congenital / Q000196:embryology*; D018811:Maternal Exposure / Q000009:adverse effects; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D012756:Sheep
chemical_list: D003907:Dexamethasone