Atrial natriuretic factor (ANF) is a smooth muscle relaxant. This thesis examined the effects of ANF on rat uterus. ANF inhibited the motor activity of non-gravid but not of the gravid uterus. This decrease in the tocolytic effects of ANF during pregnancy correlated with an increase in plasma progesterone. The tocolytic activity of ANF was also inhibited by exogenous progesterone. In contrast, the sensitivity of the uterus of both virgin and pregnant rats was significantly increased by the progesterone receptor antagonist, RU486. The inhibition of the tocolytic activity of ANF by ovariectomy was reversed by estrogen. Refractoriness to the tocolytic activity of ANF was accompanied by decreases in myometrial ANF receptors and in the stimulant effects of ANF on myometrial particulate guanylate cyclase activity and cyclic guanosine 3$ sp prime$:5$ sp prime$-monophosphate. In contrast, estrogen and RU486 increased myometrial ANF receptors. It is concluded that the exposure of the myometrium to progesterone during pregnancy results in the down-regulation of myometrial ANF receptors, and in turn in a decrease in its tocolytic and biochemical effects on the uterus; this may be physiologically important for the progression of pregnancy and parturition.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.70258 |
| Date | January 1992 |
| Creators | Potvin, William |
| 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 Pharmacology and Therapeutics.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001266028, proquestno: AAINN74476, Theses scanned by UMI/ProQuest. |
Page generated in 0.0021 seconds