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This Article Full Text Full Text (PDF) All Versions of this Article: 90/6/837    most recent expphysiol.2005.031195v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Chappellaz, M. L Articles by Smith, F. G Search for Related Content PubMed PubMed Citation Articles by Chappellaz, M. L Articles by Smith, F. G Related Collections Placental-Perinatal

¹ Departments of Physiology and Biophysics/Medicine, University of Calgary, Calgary, Alberta, Canada T2N 4N1

The present experiments were designed to measure the effects of acute administration of angiotensin (ANG) II on mean arterial pressure (MAP) and renal blood flow (RBF) in conscious, chronically instrumented lambs at two different stages of postnatal maturation, and to determine the receptors through which these effects of ANG II are elicited. Experiments consisted of haemodynamic measurements for 10 s before (Control) and for 60 s after intravenous (I.V.) administration of one of 11 doses of ANG II (0–200 ng kg^–1). Administration of ANG II was associated with a dose-dependent increase in MAP to a maximal effective concentration (EC₁₀₀) of 100 ng kg^–1 in lambs aged 1 and 6 weeks. Administration of ANG II has caused a dose-dependent decrease in RBF, with EC₁₀₀ values of 50 ng kg^–1 in 1-week-old lambs, and 25 ng kg^–1 in 6-week-old lambs. Responses to ANG II at the EC₅₀ were also measured in the presence of the specific ANG II AT₁ receptor antagonist, ZD 7155, the specific AT₂ receptor antagonist, PD 123319, and vehicle. Administration of ZD 7155, but not PD 123319 or vehicle, abolished the MAP and RBF responses to ANG II in both age groups. In addition, MAP decreased and RBF increased in both age groups after administration of ZD 7155, but not PD 123319; the effects were similar in both age groups. These data provide new information that pressor and renal vasoconstrictor effects of ANG II during the first 6 weeks of postnatal life in lambs are elicited by activation of AT₁ but not AT₂ receptors.

(Received 15 June 2005; accepted after revision 3 August 2005; first published online 9 August 2005)
Corresponding author F. G. Smith: Department of Physiology and Biophysics, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1. Email: fsmith{at}ucalgary.ca