Full Text Available
Note: Clicking the button above will open the full text document at the original institutional repository in a new window.
The role of Ca²⁺ and cAMP in GnRH-stimulated LH release
In this thesis a detailed study of the kinetics of GnRH-stimulated LH release was made. GnRH stimulated LH release in a biphasic manner. During the first 3 minutes of stimulation, there was a transient spike phase of release followed by plateau phase of lower amplitude. Both phases of release are la...
Saved in:
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Language: | English |
| Published: |
Division of Chemical Pathology
2018
|
| Subjects: | |
| Tags: |
No Tags, Be the first to tag this record!
|
| _version_ | 1867613253230657536 |
|---|---|
| access_status_str | Open Access |
| author | Wakefield, Ian Kurt |
| author2 | Davidson, James S |
| author_browse | Davidson, James S Wakefield, Ian Kurt |
| author_facet | Davidson, James S Wakefield, Ian Kurt |
| author_sort | Wakefield, Ian Kurt |
| collection | Thesis |
| description | In this thesis a detailed study of the kinetics of GnRH-stimulated LH release was made. GnRH stimulated LH release in a biphasic manner. During the first 3 minutes of stimulation, there was a transient spike phase of release followed by plateau phase of lower amplitude. Both phases of release are largely dependent on extracellular Ca²⁺. The spike phase of release is dependent on Ca²⁺ entry via a receptor-operated Ca²⁺ channel (ROCC) (about 90%) and on the mobilization of intracellular Ca²⁺ stores. The role of ROCC were examined by using ruthenium red which inhibits both ROCC and voltage-sensitive Ca²⁺ channels (VSCC). VSCC are not involved in the spike phase of GnRH-stimulated LH release since D600 and nifedipine, inhibitors of VSCC, have no effect on the spike phase. The plateau phase of release is dependent on Ca²⁺ entry via VSCC (about 50%) and ROCC (about 50%). Forskolin, an activator of adenylate cyclase, was used to investigate the role of cAMP in LH release. Forskolin stimulated an increase in both LH release and cellular cAMP levels. GnRH was also able to elevate the cellular CAMP concentration. GnRH interacted synergistically with forskolin to stimulate LH release. The synergism between GnRH and forskolin was not due to an interaction at (1) the GnRH receptor, (2) the level of intracellular Ca²⁺ mobilization, or (3) inositol phosphate metabolism. However, forskolin was able to synergistically interact with secretagogues that increase the cytosolic Ca²⁺ concentration and activators of protein kinase C. This suggested that forskolin was interacting with GnRH at a site distal to the activation of the Ca²⁺ second messenger system and protein kinase C. The data suggest that the initial response to GnRH is largely Ca²⁺-dependent and that other second messengers, if active, play a minor role. cAMP is thought to play a modulatory role and may be involved in the maintenance of secretion. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/27120 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:33:12.104Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2018 |
| publishDateRange | 2018 |
| publishDateSort | 2018 |
| publisher | Division of Chemical Pathology |
| publisherStr | Division of Chemical Pathology |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/27120 The role of Ca²⁺ and cAMP in GnRH-stimulated LH release Wakefield, Ian Kurt Davidson, James S King, Judy A Chemical Pathology Cyclic AMP - analysis Gonadotropins. Receptors, Gonadoliberin. Calcium - analysis In this thesis a detailed study of the kinetics of GnRH-stimulated LH release was made. GnRH stimulated LH release in a biphasic manner. During the first 3 minutes of stimulation, there was a transient spike phase of release followed by plateau phase of lower amplitude. Both phases of release are largely dependent on extracellular Ca²⁺. The spike phase of release is dependent on Ca²⁺ entry via a receptor-operated Ca²⁺ channel (ROCC) (about 90%) and on the mobilization of intracellular Ca²⁺ stores. The role of ROCC were examined by using ruthenium red which inhibits both ROCC and voltage-sensitive Ca²⁺ channels (VSCC). VSCC are not involved in the spike phase of GnRH-stimulated LH release since D600 and nifedipine, inhibitors of VSCC, have no effect on the spike phase. The plateau phase of release is dependent on Ca²⁺ entry via VSCC (about 50%) and ROCC (about 50%). Forskolin, an activator of adenylate cyclase, was used to investigate the role of cAMP in LH release. Forskolin stimulated an increase in both LH release and cellular cAMP levels. GnRH was also able to elevate the cellular CAMP concentration. GnRH interacted synergistically with forskolin to stimulate LH release. The synergism between GnRH and forskolin was not due to an interaction at (1) the GnRH receptor, (2) the level of intracellular Ca²⁺ mobilization, or (3) inositol phosphate metabolism. However, forskolin was able to synergistically interact with secretagogues that increase the cytosolic Ca²⁺ concentration and activators of protein kinase C. This suggested that forskolin was interacting with GnRH at a site distal to the activation of the Ca²⁺ second messenger system and protein kinase C. The data suggest that the initial response to GnRH is largely Ca²⁺-dependent and that other second messengers, if active, play a minor role. cAMP is thought to play a modulatory role and may be involved in the maintenance of secretion. 2018-01-30T13:37:37Z 2018-01-30T13:37:37Z 1991 Master Thesis Masters MSc (Med) http://hdl.handle.net/11427/27120 eng application/pdf Division of Chemical Pathology Faculty of Health Sciences University of Cape Town |
| spellingShingle | Chemical Pathology Cyclic AMP - analysis Gonadotropins. Receptors, Gonadoliberin. Calcium - analysis Wakefield, Ian Kurt The role of Ca²⁺ and cAMP in GnRH-stimulated LH release |
| thesis_degree_str | Master's |
| title | The role of Ca²⁺ and cAMP in GnRH-stimulated LH release |
| title_full | The role of Ca²⁺ and cAMP in GnRH-stimulated LH release |
| title_fullStr | The role of Ca²⁺ and cAMP in GnRH-stimulated LH release |
| title_full_unstemmed | The role of Ca²⁺ and cAMP in GnRH-stimulated LH release |
| title_short | The role of Ca²⁺ and cAMP in GnRH-stimulated LH release |
| title_sort | role of ca²⁺ and camp in gnrh stimulated lh release |
| topic | Chemical Pathology Cyclic AMP - analysis Gonadotropins. Receptors, Gonadoliberin. Calcium - analysis |
| url | http://hdl.handle.net/11427/27120 |
| work_keys_str_mv | AT wakefieldiankurt theroleofca2andcampingnrhstimulatedlhrelease AT wakefieldiankurt roleofca2andcampingnrhstimulatedlhrelease |