This thesis focuses on the renin-angiotensin system and atrial natriuretic factors (ANF) two hormonal systems which are stimulated and which may exert important antagonizing actions on the regulation of mean arterial pressure (MAP) and body fluid homeostasis during pregnancy. All experiments were conducted in healthy nonpregnant and/or pregnant (gestational age of 105 to 140 days, term = 145 days) mixed breed ewes, using a facility designed for studies of large animals. Findings from the first study with unilateral denervated kidneys provide evidence that renal nerves are a necessary component in the control of renin secretion in both nonpregnant and pregnant ewes. The second study demonstrates that angiotensin II (AngII) and ANF do not account for the dramatic suppression of renin secretion in response to the reduction of renal perfusion pressure in sheep with bilateral renal denervation. The data from these two studies suggest that the renal baroreceptors influence renin secretion indirectly through activation of renal afferents rather than by a direct action on the juxtaglomerular apparatus. In order to study the possible effects of increased plasma AngII on ANF production during pregnancy, four doses of AngII (0.5, 5, 20, 40 ng/kg/min) and nitroprusside were simultaneously infused to separate indirect hemodynamic actions on ANF secretion from direct hormonally mediated effects on ANF secretion by AngII. The data clearly show that AngII increases plasma ANF in a dose-dependent manner but: only in the presence of the AngII pressor effect. A striking finding was the demonstration that the natriuretic and diuretic responses to intrarenal artery infusion of three doses of ANF (0.3, 1.5, 3.0 pmol/kg/min) are increased during ovine pregnancy and these responses are solely limited to actions on the distal part of the nephron without altering renal vascular or glomerular function. Finally, a study with 10 days of intrarenal artery infusion of low dose AngII (1 ng/kg/m
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.39904 |
| Date | January 1995 |
| Creators | Fan, Li, 1967- |
| Contributors | Quillen, Ed. W. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Physiology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001480955, proquestno: NN12364, Theses scanned by UMI/ProQuest. |
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