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Title: Post translational control of luteinizing hormone secretion
Author: Currie, R. J. W.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1994
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The investigations detailed in this thesis were undertaken to determine the mechanisms regulating the post translational control of LH secretion in the ewe. LH is stored within dense core secretory granules in the gonadotrophs of the adenohypophysis. Studies on cellular ultrastructure and gene expression were conducted on pituitary glands obtained from Welsh mountain ewes at points throughout the oestrous cycle. In order to determine if a structural priming response of gonadotrophin granules in preparation for the preovulatory LH surge was present in the sheep, fixed pituitary tissue was examined using immunogold labelling techniques under the electron microscope. In luteal phase, 20% of gonadotrophs possessed granules located in one aspect of the cytoplasm juxtaposed to the nearest sinusoid, leading to the appearance of a polarised cell. The percentage of polarised cells increased throughout the cycle, reaching a peak of 90% in mid LH surge. Stereological analysis of granule diameter showed that exocytosis occurred in a size dependent manner. Initial secretion occurred from the 158-180nm size class with the larger granules released only during the preovulatory LH surge. LHβ mRNA abundance decreased from luteal through follicular phase, reaching its lowest value during the surge. The replenishment of intracellular LH stores occurred initially via the synthesis of the smaller granule size classes, first visible in the cytoplasm 48h after an induced LH surge. As cells refined, displaying a morphology similar to a typical luteal phase gonadotroph at 96h post surge, the diameter of granules synthesized increased, approaching values observed in the late luteal phase. Throughout the refill phase, LHβ mRNA abundance did not change.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available