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Compartmentalization of human chorionic gonadotrophin sensitivity and luteinizing hormone receptor mRNA in different subtypes of the human corpus luteum
Umeå University, Faculty of Medicine, Department of Clinical Sciences, Obstetrics and Gynaecology.
Umeå University, Faculty of Medicine, Department of Clinical Sciences, Obstetrics and Gynaecology.
Umeå University, Faculty of Medicine, Department of Clinical Sciences, Obstetrics and Gynaecology.
Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
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1997 (English)In: Human Reproduction, ISSN 0268-1161, E-ISSN 1460-2350, Vol. 12, no 5, 1037-1042 p.Article in journal (Refereed) Published
Abstract [en]

The relationship was investigated between different ultrasonographically defined subtypes of the human corpus luteum and progesterone production. Twenty-one women in the mid-luteal phase who underwent laparotomy for benign uterine conditions volunteered for this study. The corpus luteum was identified by preoperative ultrasound and classified into four types according to earlier established criteria, where types a and c were centrally hypoechoic, types b and d were centrally echogenic, types a and b had thin surrounding 'walls' (<3 mm) and types c and d had thick walls (<3 mm). After luteectomy, the theca externa capsule was removed and tissue from directly beneath the surface ('peripheral region') and the layer immediately beneath ('inner region') minced into 4-6 mg pieces. Following preincubation, pieces were incubated for 3 h at 37 degrees C in HEPES-minimal essential medium buffer with or without human chorionic gonadotrophin (HCG; 10 IU/ml), and subsequently progesterone accumulation in the medium was determined by radioimmunoassay. The highest progesterone production was consistently seen in the peripheral region. Type a had a significantly (P > 0.01) lower progesterone production (3.2 +/- 1.5 nmol/g tissue wet weight, mean +/- SEM, n = 4) than that of types b, c and d (17.7 +/- 3.5 nmol/g tissue wet weight, n = 9). All types responded to HCG with an almost two-fold increase in progesterone production. However, the maximal progesterone produced following stimulation by HCG in the type a corpus luteum was <50% of the basal (unstimulated) progesterone synthesis of any other type of corpus luteum. Using in-situ hybridization, with a primate RNA probe complementary to the region coding the extracellular part of the luteinizing hormone (LH) receptor, a highly localized expression of LH receptor mRNA to the peripheral region was found. Negligible or low levels of expression were found in the theca externa capsule and the inner region. No obvious correlations between the different subtypes of corpora lutea and LH receptor mRNA expression were seen. Thus, the ultrasonographic detection of a thin-walled and centrally hypoechoic corpus luteum correlates well with reduced progesterone secretion. The underlying cellular mechanism does not appear to involve a diminished sensitivity to the gonadotrophic stimulation by LH or HCG.

Place, publisher, year, edition, pages
1997. Vol. 12, no 5, 1037-1042 p.
National Category
Obstetrics, Gynecology and Reproductive Medicine
Identifiers
URN: urn:nbn:se:umu:diva-41634DOI: 10.1093/humrep/12.5.1037PubMedID: 9194662OAI: oai:DiVA.org:umu-41634DiVA: diva2:407407
Available from: 2011-03-30 Created: 2011-03-30 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Intraovarian mechanisms influencing the human corpus luteum
Open this publication in new window or tab >>Intraovarian mechanisms influencing the human corpus luteum
2000 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Introduction: The human corpus luteum (CL) is a transient endocrine gland, only functionally active for about 14 days. Its principal function is to produce and secrete progesterone and thereby support the endometrium for implantation of a blastocyst and prevent rejection of the developing embryo. In the event of a non-conceptive cycle, functional and structural demise of the CL follows and a new ovulatory cycle begins. The aims of the thesis were to study different mechanisms involved in the extrinsic and intrinsic regulation of the CL and correlate these findings to available clinical investigations tools.

Materials and methods: Sixty women volunteered to donate their CL prior to scheduled surgery due to benign conditions. They were grouped according to CL-age, based on the occurrence of a preovulatory luteinizing hormone (LH) surge where days 2-5 post LH surge were designated as early luteal phase, days 6-9 as mid luteal phase and days 11-14 as late luteal phase. The CL bearing ovary was investigated using transvaginal ultrasonographical B-mode and color Doppler imaging prior to surgery. Following excision, the CL was further characterized using anatomical and morphological measurements, in vivo and in vitro hormone synthesis, isolation and cultures of steroidogenic luteal cells. Moreover, active transcription of putative regulatory genes of interest was targeted using semi-quantitative reverse-transcription polymerase chain reaction, in situ hybridization and Northern blots, and these genes' respective translation products were characterized by immunocytochemistry.

Results: The bulk of progesterone is stimulated by human chorionic gonadotropin (hCG) in the peripheral (steroidogenic) layer of the CL, where the LH/hCG receptor, as well as progesterone receptor (PR) isoform A/B and estrogen receptor type β (ER-β), but not ER-α, was localized. The sesitivity towards hCG was highest during the mid luteal phase in concordance with the value of LH/hCG receptor coding mRNAs. During this phase, despite low levels of PR-B mRNA, hCG treatment initiated a significant rise in progesterone output which could be blunted by the PR antagonist mifepristone. Increased amounts of prostaglandin (PG) F and its respective receptor (FP) mRNA were detected during the later developmental stages of the CL. However, steroidogenic luteal cells were unresponsive to added PGF until late luteal phase, indicative of an acquisition of sensitivity to the proposed luteolytic signal during this stage. Intraluteal vascular density was highest in early luteal phase and dramatically decreased during the course of CL development, a finding which was inversely correlated to resistance to blood flow in intraovarian blood vessels supplying the CL. Furthermore, a high degree of agreement between ultrasonographical and anatomical measurements of the CL was found.

Conclusions: Based on the novel findings herein, the hypothesis of steroid influence, acting within or near the steroidogenic luteal cells is confirmed. Alongside the classical extrinsic signals (e.g. hCG) and locally produced factors (e.g. PGF) these findings may further explain their modulatory roles during luteolysis or very early pregnancy. Furthermore, transvaginal ultrasonography in combination with color Doppler measurements may serve as a clinical tool to evaluate CL function.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2000. 44 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 695
Keyword
Corpus luteum, steroidreceptors, progesterone, LH/hCG, PGF2α, ultrasonography
National Category
Obstetrics, Gynecology and Reproductive Medicine
Identifiers
urn:nbn:se:umu:diva-46975 (URN)91-7191-915-5 (ISBN)
Public defence
2000-10-27, Hörsal E04, by 6E, Norrlands universitetssjukhus, Umeå, 09:00 (English)
Opponent
Available from: 2011-09-17 Created: 2011-09-17 Last updated: 2011-09-17Bibliographically approved

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Ottander, UlrikaBäckström, TorbjörnNy, Tor

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