This thesis examines the effects of continuous theophylline pretreatment on the A$ sb2$ adenosine receptor system in cultured murine neuroblastoma cell lines, which either do or do not also express A$ sb1$ adenosine receptors. N-Ethylcarboxamido adenosine (NECA) stimulates cAMP accumulation and binds to A$ sb2$ receptors in a saturable and biphasic fashion in both types of cell cultures. Sixteen hours of theophylline treatment led to a significant increase in the number of low affinity A$ sb2$ binding sites, as well as a potentiation of NECA-stimulated cAMP accumulation, regardless of whether the cells expressed A$ sb1$ receptors. The enhanced adenylate cyclase stimulation in cells treated for 8 hours is completely blocked by addition of cycloheximide, indicating that new protein synthesis plays a role in the effects of theophylline. The potentiated response to NECA continues through 1 week of treatment in both sets of cultured cells, but disappears after 2 weeks of theophylline pretreatment in the cells expressing both A$ sb1$ and A$ sb2$ receptors. Binding profiles in cells that do not express A$ sb1$ receptors demonstrate that while control cells are sensitive to the effects of the non-hydrolyzable analogue of guanosine triphosphate, Gpp(NH)p, cells that were treated for 4 days or 1 week with theophylline are no longer sensitive to the effects of this compound. This could indicate either an enhanced coupling between the receptor and the stimulatory guanine nucleotide regulatory protein (G$ rm sb{s}$ protein) or a complete uncoupling of these two proteins. There is a significant decrease in the basal cAMP levels after 4 days or more of treatment, as well as an increase in the immunoreactivity of the $ alpha$ subunit of the stimulatory G protein after 2 weeks of treatment. Taken together, these findings would tend to favour the possibility of enhanced coupling between the receptor and the G$ rm sb{s}$ protein. Cells that express both receptor subtypes also show
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.28668 |
| Date | January 1994 |
| Creators | Babey, Anna Marie |
| Contributors | Palmour, Roberta M. (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 Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001462759, proquestno: NN05666, Theses scanned by UMI/ProQuest. |
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