Thesis (PhD)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: This study investigated the effect of several hormones on the rat corticosteroid binding
globulin proximal promotor and for the first time showed that modulation occurs at the
promotor level and can be correlated with changes in corticosteroid binding globulin
mRNA and protein levels. The effect of various physical and psychological stressors on
rat liver corticosteroid binding globulin mRNA levels was also tested and it was shown
that voluntary running had no effect on rat corticosteroid binding globulin levels but
that involuntary swimming and immobilization decreased rat corticosteroid binding
globulin mRNA levels. Glucocorticoid responsiveness of the corticosteroid binding
globulin promoter was investigated further by using truncated contructs of the
corticosteroid binding globulin proximal promoter. Glucocorticoid responsiveness was
delineated to between -296 and -145bp from the transcription start site an area that
contains putative binding sites for D-site binding protein, hepatic nuclear factor-3 and
CAAT/enhancer binding protein suggesting that these transcription factors may be
involved in glucocorticoid responsiveness of the corticosteroid binding globulin
proximal promoter.
The dissociative glucocorticoid activity of medroxyprogesterone acetate and Compound
A, both putative dissociated glucocorticoids, was compared to standard glucocorticoids
by examining transactivation of glucocorticoid response element-containing reporter
constructs and transrepression of corticosteroid binding globulin gene expression in
hepatic cell lines. Results showed that medroxyprogesterone acetate, but not Compound
A, trans activates only in the presence, but not in the absence, of co-transfected
glucocorticoid receptor. Medroxyprogesterone acetate down modulated dexamethasone
transactivation while the modulatory effect of Compound A depends on the order of addition of Compound A. If added together Compound A has no effect on
dexamethasone transactivation, however, if Compound A was added before
dexamethasone, Compound A significantly decreased dexamethasone transactivation.
Both medroxyprogesterone acetate and Compound A, like glucocorticoids,
transrepressed the rat corticosteroid binding globulin proximal promoter. The potency
of repression was similar but Compound A repressed with a higher efficacy than
medroxyprogesterone acetate. We conclude that Compound A is a completely
dissociated glucocorticoid in contrast to medroxyprogesterone acetate that displays only
partial dissociation, which is dependent on glucocorticoid receptor levels. / AFRIKAANSE OPSOMMING: Tydens hierdie ondersoek is die effek van verskeie hormone op die rot kortikosteroied
bindings globulien proksimale promoter ondersoek en vir die eerste keer is getoon dat
modulering plaasvind op promoter-vlak en dat repressie korrileer met die verandering in
kortikosteroied bindings globulien mRNA-en proteinvlakke. Die effek van verskeie
fisiese en fisiologiese stressors op rotlewer kortikosteroied bindings globulien-mRNAvlakke
is ook getoets en daar is getoon dat willekeurige hardloop geen effek op rot
kortikosteroied bindings globulien-mRNA-vlakke het nie maar dat gedwonge swem en
immobilisering rot kortikosteroied bindings globulien-mRNA-vlakke verlaag.
Glukokortikoied responsiewiteit van die kortikosteroied bindings globulien proksimale
promoter is verder ondersoek deur verkorte konstrukte van die kortikosteroied bindings
globulien te toets. Glukokotikoied responsiewiteit is afgebaken tot tussen -296 en -
145bp vanaf die transkripsie beginplek 'n area wat beweerde bindings setels vir D-setel
bindings protein, hepatosiet faktoor-3 en CCAAT-bindings protein-2 bevat en dus
suggereer dat hierdie transkripsie faktore betrokke mag wees met glukokortikoied
effekte op die kortikosteroied bindings globulien-proksimale promoter.
Die dissosiatiewe glukokortikoied aktiwiteit van medroksiprogesteroon asetaat en
Verbinding A, beide beweerde dissosiatiewe glukokortikoiede, relatief tot standaard
glukokortikoiede is vergelyk deur transaktivering van glukokortikoied reseptor
e1elment-bevattende konstrukte en onderdrukking van kortikosteroied bindings
globulien geen ekspressie in lewersellyne te bestudeer. Medroksiprogesteroon asetaat,
maar nie Verbinding A nie, transaktiveer slegs in die teenwoordigheid, maar nie in die
afwesigheid, van ko-getransfekteerde glukokortikoied reseptore. Medroksiprogesteroon
asetaat moduleer deksametasoon transaktivering afwaarts terwyl die modulerende effek van Verbinding A afhanklik van die orde van Verbinding A byvoeging is. Indien saam
bygevoeg het Verbinding A geen effek op deksametasoon transaktivering nie, maar
indien Verbinding A voor deksametasoon bygevoeg word verlaag Verbinding A
deksametasoon transaktivering. Beide medroksiprogesteroon asetaat and Verbinding A,
soos glukokortikoiede, onderdruk die rot kortikosteroied bindings globulien-proksimale
promoter. Die sterkte van onderdrukking is dieselfde maar Verbinding A onderdruk met
'n hoër effektiwiteit as medroksiprogesteroon asetaat. Ons toon dat Verbinding A 'n
totale dissosiatiewe glukokortikoied is in teenstelling met medroksiprogesteroon asetaat,
wat slegs gedeeltelik dissosiatief is afhangende van glukokortikoied reseptor-vlakke.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53475 |
| Date | 12 1900 |
| Creators | Allie-Reid, Fatima |
| Contributors | Louw, A., Hapgood, J. P., Swart, P., Stellenbosch University. Faculty of Science. Dept. of Biochemistry. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 179 p. |
| Rights | Stellenbosch University |
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