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| 2. |
- Kirilovas, Dmitrijus, et al.
(författare)
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Conversion of circulating estrone sulfate to 17β-estradiol by ovarian tumor tissue : A possible mechanism behind elevated circulating concentrations of 17β-estradiol in postmenopausal women with ovarian tumors
- 2007
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Ingår i: Gynecological Endocrinology. - : Informa UK Limited. - 0951-3590 .- 1473-0766. ; 23:1, s. 25-28
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Tidskriftsartikel (refereegranskat)abstract
- AIM: Elevated serum levels of 17beta-estradiol (E2) are frequently found in postmenopausal women with ovarian tumors not classified as estrogen-producing. Conversion of circulating estrone sulfate (E1S) to E2 is one alternative way of E2 formation in target tissues in postmenopausal women. Our aim was to find out if conversion of circulating E1S to E2 by the tumor tissue could be a reason for elevated serum E2 levels in postmenopausal women with 'non-estrogen-producing' ovarian tumors. METHOD: Serum E2 was measured in 12 postmenopausal women with 'non-estrogen-producing' ovarian tumors (nine benign, three malignant). Total hydrolysis of and [3H]E2 formation from [3H]E1S by the tumor tissue homogenates was studied in vitro. RESULTS: Serum E2 showed significant positive correlations with total hydrolysis of and [3H]E2 formation from [3H]E1S in the total material as well as in the benign tumor subgroup. [3H]E2 formation was the most important independent variable. CONCLUSION: Conversion of circulating E1S to E2 by the tumor tissue could be one important reason for elevated S-E2 levels in postmenopausal women with 'non-estrogen-producing' ovarian tumors.
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| 3. |
- Kirilovas, Dmitrijus, et al.
(författare)
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Granulosa cell aromatase enzyme activity : Effects of follicular fluid from patients with polycystic ovary syndrome, using aromatase conversion and [11C]vorozole-binding assays
- 2006
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Ingår i: Gynecological Endocrinology. - : Informa UK Limited. - 0951-3590 .- 1473-0766. ; 22:12, s. 685-691
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Tidskriftsartikel (refereegranskat)abstract
- The local regulation of ovarian aromatase enzyme in polycystic ovary syndrome (PCOS) was studied with aromatase conversion and [C-11]vorozole-binding assays to analyze aromatase activity, substrate-enzyme affinity and number of aromatase binding sites in non-cultured human granulosa cells (GC) incubated with different sources and preparations of follicular fluid (FF). Incubation with FF from women stimulated in in vitro fertilization cycles with follicle-stimulating hormone yielded higher conversion activity than with FF from healthy women and PCOS patients, paralleled with higher substrate affinity (lower K-d) than with FF from healthy women. In PCOS women, charcoal-pretreated FF yielded higher conversion, whereas the ether-pretreated FF yielded lower conversion activity, than with untreated PCOS FF. Both preparations of FF yielded higher affinity to substrate (lower Kd values) and the ether-pretreated FF a lower number of binding sites (B-max). It seems that steroids with the presence of proteins in PCOS FF reduced aromatase conversion activity through decreased substrate affinity, whereas FF preparations devoid of proteins reduced the aromatase conversion activity mainly through blocking of aromatase active sites. Identification of specific agents responsible for this rapid regulation of aromatase function might help to understand normal regulation of the menstrual cycle and supposed imbalances of inhibitors/activators in PCOS.
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| 4. |
- Kirilovas, Dmitrijus, 1962-
(författare)
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Regulation of Ovarian Aromatase: Studies by Aromatase Assays in vitro and in vivo
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- An in vitro method was developed for measuring aromatase, based on binding of competitive aromatase inhibitor [11C]vorozole to the active site of the enzyme. [11C]Vorozole displayed high, specific binding in vitro to human placenta and human granulosa cells (GC), both fresh and frozen/thawed cells, provided correct procedures were used. High, specific binding was also observed in pig and rat ovaries, whereas binding in other tissues was unspecific and usually low. Aromatase concentrations measured by [11C]vorozole binding correlated well to aromatase activity measured by [3H]water release from 1β[3H]androstenedione. In human GC in vitro, low concentrations of 5α-dihydrotestosterone (DHT), but not of other androgens, stimulated aromatase activity measured by [3H]water release but had no effects on aromatase concentration measured by [11C]vorozole binding. DHT may interact with aromatase differently than other androgens, perhaps by changing aromatase affinity to precursor. In the rat estrous cycle, aromatase activity in ovarian homogenate, measured by [3H]water release, together with serum androstenedione and estradiol-17β, peaked between 6 and 13 h after onset of the light period of proestrus, the former activity being independent of radioactive substrate concentration. [11C]Vorozole binding characteristics changed more rapidly than de novo synthesis of the enzyme. [11C]Vorozole binding Kd showed close inverse correlation to aromatase activity in ovarian homogenate and to serum estradiol-17β. Rapid changes in substrate affinity rather than changes in substrate concentration or de novo synthesis of the enzyme may thus be important for regulation of ovarian aromatase. The [11C]vorozole in vivo technique yields additional information compared with traditional in vitro techniques.
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| 5. |
- Kushnir, Mark M, et al.
(författare)
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Steroid profiles in ovarian follicular fluid from regularly menstruating women and women after ovarian stimulation
- 2009
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Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 55:3, s. 519-526
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Information on the concentrations of steroids in ovarian follicular fluid (FF) from regularly menstruating (RM) women has been limited because of the absence of methods for the simultaneous quantification of multiple steroids in small volumes of FF. We studied steroid profiles in FF during the early follicular phase of the menstrual cycle and after ovarian stimulation for in vitro fertilization (IVF), and compared concentrations with published values obtained by immunoassay (IA). METHODS: We used liquid chromatography-tandem mass spectrometry (LC-MS/MS) to measure 13 steroids in 40-microL aliquots of FF samples from 21 RM women and from 5 women after ovarian stimulation for IVF. Relationships between concentrations of steroids and their ratios (representations of the enzyme activities) were evaluated within and between subgroups. RESULTS: The concentrations of testosterone (Te), androstenedione (A4), and estradiol (E2) measured by LC-MS/MS were lower than those previously reported in studies with IAs. In RM women, androgens were the most abundant class of steroids, with A4 being the major constituent. The concentrations of 17-hydroxyprogesterone (17OHP), total androgens, and estrogens were 200- to 1000-fold greater in FF than in serum. Compared with RM women, FF samples from women undergoing ovarian stimulation had significantly higher concentrations of E2 (P = 0.021), pregnenolone (P = 0.0022), 17OHP (P = 0.0007), and cortisol (F) (P = 0.0016), and significantly higher ratios of F to cortisone (P = 0.0006), E2 to estrone (P = 0.0008), and E2 to Te (P = 0.0013). CONCLUSIONS: The data provide the first MS-based concentration values for 13 steroids in ovarian FF from RM women, from estrogen- and androgen-dominant follicles, and from women after ovarian stimulation for IVF.
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| 7. |
- Naessén, Tord, et al.
(författare)
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Steroid profiles in ovarian follicular fluid in women with and without polycystic ovary syndrome, analyzed by liquid chromatography-tandem mass spectrometry.
- 2010
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Ingår i: Fertility and Sterility. - : Elsevier BV. - 0015-0282 .- 1556-5653. ; 94:6, s. 2228-2233
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE To compare steroid concentrations and steroid product-to-precursor ratios in ovarian follicular fluid (FF) from women with polycystic ovary syndrome (PCOS) and from regularly menstruating women in their early follicular phase, using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Polycystic ovary syndrome involves abnormal regulation of the steroidogenic enzymes, leading to arrest of follicle development. DESIGN Case-control study. SETTING University hospital clinic. PATIENT(S) Follicular fluid from size-matched ovarian follicles (5-8 mm) in 27 nonstimulated women with PCOS and in 21 women without PCOS was sampled. Thirteen steroids were quantitated from 40 muL of FF, using LC-MS/MS. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) Concentrations of steroids in the FF and product-to-precursor ratios (enzyme activity) were compared between the groups. RESULT(S) In women with PCOS, ovarian FF contained higher concentrations of individual and total androgens, lower individual and total estrogens (E), and a lower total E-to-androgen ratio, compared with regularly menstruating women. The product-to-precursor concentration ratios indicated higher CYP17-linked and lower CYP19-linked (aromatase) enzyme activity. Receiver operating characteristic plots indicated the early CYP17 step (17-OH5P/5P) being highly important for the prevalence of PCOS (c = 0.95). CONCLUSION(S) The women with PCOS had higher ovarian CYP17-linked and lower CYP19-linked (aromatase) enzyme activity, confirming previous data. Multiple steroid assessments from minute volumes including FF from nonstimulated ovaries, using LC-MS/MS, might be useful in research, clinical endocrinology, and in IVF.
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