Angiotensin II receptor (type 1 and 2) expression peaks when placental growth is maximal in sheep.
In sheep, placental size is maximal by midgestation, but blood flow continues to increase until term. No nerves are present and ANG II is thought to be a major regulator of vascular tone. We hypothesized that angiotensin type 2 receptors (AT(2)) would predominate over type 1 (AT(1)) until late in gestation and be primarily expressed in the vasculature. Real-time PCR, hybridization histochemistry, and ligand-binding studies were performed on placentae and fetal membranes at 27, 45, 66 +/- 1, 100 +/- 4, 130, and 140 days of gestation (term approximately 150 days) to determine quantitative changes and localization. The maximum level of AT(1) expression occurred in the 45-day placenta and was located predominantly in the maternal stromal cells. AT(1) receptors were expressed in the endothelial cells of the chorion in the first half of pregnancy, where later in gestation, both AT(1) and AT(2) receptors were predominant in blood vessels. These results suggest that ANG II, via the AT(1) receptor, may have hitherto unsuspected important roles in the growth/function on the ovine placenta during the maximal growth phase.
Koukoulas
Irene
I
Howard Florey Institute of Experimental Physiology and Medicine, The University of Melbourne, 3010 Victoria, Australia.
Mustafa
Tomris
T
Douglas-Denton
Rebecca
R
Wintour
E Marelyn
EM
D000818:Animals; D005321:Extraembryonic Membranes / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D005865:Gestational Age; D010920:Placenta / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D010929:Placentation; D011247:Pregnancy; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin / Q000235:genetics / Q000378:metabolism*; D012756:Sheep; D017154:Stromal Cells / Q000378:metabolism; D014018:Tissue Distribution
D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin