Autoregulation of renal blood flow is mediated by two mechanisms. The myogenic response operates at $ approx$0.1-0.2 Hz and tubuloglomerular feedback (TGF) operates at $ approx$0.03-0.05 Hz. Atrial natriuretic factor (ANF) dilates pre-glomerular resistance vessels, in which autoregulation occurs, and has been reported to inhibit TGF. We tested the potential actions of ANF on TGF-mediated autoregulation using Sprague-Dawley rats anesthetized with isoflurane. Renal perfusion pressure (RPP) was manipulated by a servo-controlled clamp placed on the aorta between the renal arteries. Time constants for constriction and dilatation were consistent with operation of TGF. ANF did not affect either the magnitude or the time constants of the response. / To test the contribution of TGF resetting to the wide dynamic range of steady state autoregulation experiments, the autoregulatory range was first defined by conventional stepwise reduction of RPP. As ANG II is necessary for TGF resetting, the experiment was repeated in the presence of Losartan, a competitive ANG Il-AT$ sb1$ receptor antagonist. The results do not support the hypothesis that TGF resetting contributes to the wide dynamic range of steady state autoregulation. In fact, the lower limit of autoregulation was extended to a lower RPP. In the Losartan experiment, this shift was not apparent, suggesting that it was ANG II-dependent. (Abstract shortened by UMI.)
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.22864 |
| Date | January 1995 |
| Creators | Naguib, Raouf Edouard |
| Contributors | Cupples, W. A. (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 | Master of Science (Division of Experimental Medicine.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001467513, proquestno: MM08034, Theses scanned by UMI/ProQuest. |
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