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dc.contributor.authorLengoc, Chi Minh
dc.date.accessioned2010-09-15T03:21:16Z
dc.date.available2010-09-15T03:21:16Z
dc.date.issued1984
dc.identifier.urihttps://hdl.handle.net/10182/2522
dc.description.abstractHuman chorionic gonadotropin (hCG) (5µg) which was iodinated with ImCi Na¹²⁵ I was about 50% and 40% as potent as that which was iodinated with .25 mCi Na¹²⁵ I in radioligand receptor assay (RRA) and in vitro bioassays respectively. The amount of iodine incorporated to the hormone rather than the radioactivity was responsible for these potency losses of the radioiodinated hormone. Preincubation or incubation of porcine granulosa cells in the aqueous extract of sheep hypothalamus resulted in a decrease in the binding of ¹²⁵ I -hCG to these cells. Addition of aprotinin I (.06 - 1.5 TIU/ml) or bacitracin (2 mM) to the extract did not prevent this decrease in binding. The results indicate that the binding decrease was due to receptor occupancy by hypothalamic LH, and was not due to damage to receptors. The ability of ¹²⁵ I -hCG to displace hypothalamic LH from its receptors was dependent on the duration and conditions of the preincubation. The aqueous extract of sheep hypothalamus contained LH which behaved similarly to that of pituitary and skeletal muscle extracts in gel chromatography, RIA, RRA and in vitro bioassays. Hypothalamus including median eminence, hypothalamus minus median eminence and pituitary contained 27µg, 137ng and 1342µg respectively of immunoactive LH per gram wet weight of tissue. Basing on both RRA and in vitro bioassays, hypothalamic LH averaged about 1.5 and .5 as potent as pituitary and skeletal muscle LH respectively. Particulate fractions (1000 x g, 10000 x g and 70000 x g) of sheep hypothalamus were incapable of binding to ¹²⁵ I – oLH or ¹²⁵ I -hCG. This was thought to be due to complete occupancy of hypothalamic LH/hCG receptors by hypothalamic LH. Four techniques for dissociating LH/hCG from its receptors were tested, viz. incubation of LH/hCG - receptor complexes in 1) pH 2-3 buffer, 2) pH 7.4 buffer, 3) buffer containing an excess of free LH/hCG receptors, 4) MgCl₂, 2M buffer. The receptors uncovered by technique 4 retained full binding affinity and capacity. However, using this technique as well as the others no population of specific receptors for LH/hCG could be demonstrated in any hypothalamic fractions.en
dc.language.isoenen
dc.publisherLincoln College, University of Canterburyen
dc.rights.urihttps://researcharchive.lincoln.ac.nz/page/rights
dc.subjecthCGen
dc.subjectiodinationen
dc.subjecthormonal potencyen
dc.subjecthypothalamic LHen
dc.subjectLH/hCG-receptor dissociationen
dc.subjecthypothalamic LH/hCG receptorsen
dc.subjectluteinizing hormoneen
dc.subjectsheepen
dc.titleLuteinizing hormone in the hypothalamus of the sheep : its characteristics and binding to receptorsen
dc.typeThesisen
thesis.degree.grantorUniversity of Canterburyen
thesis.degree.levelDoctoralen
thesis.degree.nameDoctor of Philosophyen
lu.thesis.supervisorIrvine, C. H. G.
lu.thesis.supervisorLivesey, J.
lu.contributor.unitDepartment of Wine, Food and Molecular Biosciencesen
dc.rights.accessRightsDigital thesis can be viewed by current staff and students of Lincoln University only. Print copy available for reading in Lincoln University Library. en
dc.subject.anzsrc060802 Animal Cell and Molecular Biologyen
dc.subject.anzsrc0601 Biochemistry and Cell Biologyen
dc.subject.anzsrc060601 Animal Physiology - Biophysicsen
dc.subject.anzsrc110306 Endocrinologyen


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