Oestrogen receptors in women and the effect of an antioestrogen, tamoxifen

Lunan, Charles Burnett (1975) Oestrogen receptors in women and the effect of an antioestrogen, tamoxifen. MD thesis, University of Glasgow.

Abstract

Oestrogen receptors in the human female genital tract; have been studied both in vitro and in vivo. The uptake of 3H-oestradiol into endometrium from different uterine areas was shown to be variable with a tendency for the highest uptake by endometrium from the lower body area of the uterus. Characterisation of the receptors from the different endometrial areas by sucrose density gradients and equilibration assays failed to reveal any difference among the receptors. In vitro conversion of a small amount of 3H-oestradiol to 3H-oestrone was demonstrated in these experiments, A critical examination of the variable factors in the techniques of determining the uptake of 3H-oestradiol into the endometrium was carried out by measuring the effect of changing 3H-oestradiol concentration in the incubation medium and by varying the duration of incubation. The reliability of the technique was tested by replicate sample incubation experiments, Myometrial and fibroid receptors were characterised by equilibration studies, and sucrose density gradient was carried out on a fibroid cytosol sample. The characteristics of these receptors were similar to those of the endometrial receptors. The uptake of 3H-oestradiol in vitro by fibroid cytosol was higher than by adjacent myometrium. Tamoxifen, a new antioestrogen, was shown to block the uptake of 3H-oestradiol by endometrium in tissue incubation. Equilibration studies of the cytosol receptors' affinity for tamoxifen showed an association constant (KA) less than one-hundredth that of oestradiol. Incubation of cytosol prepared from histologically normal endometrium showed higher levels of available receptors in proliferative than secretory phase cytosol, with effective blockage of the receptors by unlabelled oestradiol and tamoxifen. Studies were also carried out on cytosol from abnormal endometrium, and showed variable levels of receptor content even within histologically similar groups. The in vivo studies involved administration of around 50 muCi to 12 women prior to hysterectomy. In addition to measurements of uptake by endometrium, total tissue radioactivity was also measured in myometrium, cervix, Fallopian tube, ovary and vagina and the skin, muscle sheath and adipose tissue as available. The uptake was highest in the endometrium and next highest in the myometrium. Endometrial cytosol radioactivity was nearly all specifically bound indicating low levels of unbound or loosely bound oestradiol in cytosol in vivo. The sedimentation coefficient of the oestradiol-receptor complex was determined by sucrose density gradient, and was shown to be around 4.58. An unsuccessful attempt was made to detect conversion of oestradiol to oestrone in vivo. The uptake of 3H-oestradiol by uterine fibroids in vivo was confirmed. The fibroids were found to have a higher uptake than adjacent myometrium and endometrium, confirming the in vitro studies. Four patients received pre-operative treatment with tamoxifen and showed low uptake of 3H-oestradiol into the endometrial nuclei. Although the control cases had a much higher average uptake, the range was so wide that the differences between the two groups was not statistically significant. Pre-treatment with tamoxifen produced a definite lowering of the mean total tissue uptake in myometrium (P = 0.05). It is considered that the most accurate method for measuring the effect of an antioestrogen is the in vivo administration followed by the removal of target tissue, but this is far from ideal clinically. A simpler approach, by tissue or cytosol incubation, could identify tissues with oestrogen receptors and enable evaluation of antioestrogens in therapy.

• Item Type: Thesis (MD)
• Qualification Level: Doctoral
• Additional Information: Adviser: Brian Green
• Keywords: Endocrinology
• Date of Award: 1975
• Depositing User: Enlighten Team
• Unique ID: glathesis:1975-72735
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 11 Jun 2019 11:06
• Last Modified: 11 Jun 2019 11:06
• URI: https://theses.gla.ac.uk/id/eprint/72735