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This Article Full Text Full Text (PDF) All Versions of this Article: 562/3/937    most recent jphysiol.2004.064683v1 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 Bédard, S. Articles by Brochu, M. Search for Related Content PubMed PubMed Citation Articles by Bédard, S. Articles by Brochu, M.

¹ Centre de Recherche, Hôpital Sainte-Justine, Department of Obstetrics-Gynecology and Faculty of Medicine, Université de Montréal, Québec, Canada

We previously reported that sodium restriction during pregnancy reduces plasma volume expansion and promotes intra-uterine growth restriction (IUGR) in rats while it activates the renin–angiotensin–aldosterone system (RAAS). In the present study, we proceeded to determine whether expression of the two angiotensin II (ANGII) receptor subtypes (AT₁ and AT₂) change in relation to maternal water–electrolyte homeostasis and fetal growth. To this end, pregnant (gestation day 15) and non-pregnant Sprague-Dawley rats were randomly assigned to two groups fed either normal, or Na⁺-restricted diets for 7 days. At the end of the treatment period, plasma aldosterone and renin activity as well as plasma and urine electrolytes were measured. Determinations for AT₁ and AT₂ mRNA and protein were made by RNase protection assay and photoaffinity labelling, respectively, using a number of tissues implicated in volume regulation and fetal growth. In non-pregnant rats, Na⁺ restriction decreases Na⁺ excretion without altering plasma volume, plasma Na⁺ concentration or the expression of AT₁ and AT₂ mRNA or protein in the tissues examined. In normally fed pregnant rats when compared to non-pregnant controls, AT₁ mRNA increases in the hypothalamus as well as pituitary and declines in uterine arteries, while AT₁ protein decreases in the kidney and AT₂ mRNA declines in the adrenal cortex. In pregnant rats, Na⁺ restriction induces a decrease in plasma Na⁺, an increase in plasma urea, as well as a decline in renal urea and creatinine clearance rates. Protein levels for both AT₁ and AT₂ in the pituitary and AT₂ mRNA in the adrenal cortex are lower in the Na⁺-restricted pregnant group when compared to normally fed pregnant animals. Na⁺ restriction also induces a decrease in AT₁ protein in the placenta. In conclusion, these results suggest that pregnancy may increase sensitivity to Na⁺ depletion by the tissue-specific modulation of ANGII receptors. Finally, these receptors may be implicated in the IUGR response to low Na⁺.

(Received 16 March 2004; accepted after revision 9 November 2004; first published online 11 November 2004)
Corresponding author M. Brochu: Centre de Recherche, Hôpital Sainte-Justine, 3175 Côte Ste-Catherine, Montréal, Québec, Canada H3T 1C5. Email: michele.brochu{at}umontreal.ca