Transport of estradiol-17β-glucuronide, estrone3-sulfate and taurocholate across the endoplasmic reticulum membrane: evidence for different transport systems.

  • Important reactions of drug metabolism, including UGT mediated glucuronidation and steroidsulfatase mediated hydrolysis of sulfates, take place in the endoplasmic reticulum (ER) of hepatocytes. Consequently, UGT generated glucuronides, like estradiol-17β-glucuronide, have to be translocated back into the cytoplasm to reach their site of excretion. Also steroidsulfatase substrates, including estrone-3-sulfate, have to cross the ER membrane to reach their site of hydrolysis. Based on their physicochemical properties such compounds are not favored for passive diffusion and therefore likely necessitate transport system(s) to cross the ER membrane in either direction.
  • The current study aims to investigate the transport of taurocholate, estradiol-17β-glucuronide, and estrone-3-sulfate in smooth (SER) and rough (RER) endoplasmic reticulum membrane vesicles isolated from Wistar and TR(-) rat liver. Time-dependent and bidirectional transport was demonstrated for taurocholate, showing higher uptake rates in SER than RER vesicles. For estradiol-17β-glucuronide a fast time-dependent efflux with similar efficiencies from SER and RER but no clear protein-mediated uptake was shown, indicating an asymmetric transport system for this substrate.
  • Estrone-3-sulfate uptake was time-dependent and higher in SER than in RER vesicles. Inhibition of steroidsulfatase mediated estrone-3-sulfate hydrolysis decreased estrone-3-sulfate uptake but had no effect on taurocholate or estradiol-17β-glucuronide transport. Based on inhibition studies and transport characteristics, three different transport mechanisms are suggested to be involved in the transport of taurocholate, estrone-3-sulfate and estradiol-17β-glucuronide across the ER membrane.

Substrate-dependent inhibition of organic anion transporting polypeptide 1B1: comparative analysis with prototypical probe substrates estradiol-17β-<em>glucuronide</em>, <em>estrone</em>-<em>3</em>-sulfate, and sulfobromophthalein.

Organic anion transporting polypeptide (OATP) 1B1 plays an important role in the hepatic uptake of many drugs, and the evaluation of OATP1B1-mediated drug-drug interactions (DDIs) is emphasized in the latest DDI (draft) guidance documents from U.S. and E.U. regulatory agencies. It has been suggested that some OATP1B1 inhibitors show a discrepancy in their inhibitory potential, depending on the substrates used in the cell-based assay. In this study, inhibitory effects of 14 compounds on the OATP1B1-mediated uptake of the prototypical substrates [³H]estradiol-17β-glucuronide (E₂G), [³H]estrone-3-sulfate (E₁S), and [³H]sulfobromophthalein (BSP) were studied in OATP1B1-transfected cells. Inhibitory potencies of tested compounds varied depending on the substrates. Ritonavir, gemfibrozil, and erythromycin caused remarkable substrate-dependent inhibition with up to 117-, 14-, and 13-fold difference in their IC₅₀ values, respectively.
Also, the clinically relevant OATP inhibitors rifampin and cyclosporin A exhibited up to 12- and 6-fold variation in their IC₅₀ values, respectively. Regardless of the inhibitors tested, the most potent OATP1B1 inhibition was observed when [³H]E₂G was used as a substrate. Mutual inhibition studies of OATP1B1 indicated that E₂G and E₁S competitively inhibited each other, whereas BSP noncompetitively inhibited E₂G uptake. In addition, BSP inhibited E₁S in a competitive manner, but E₁S caused an atypical kinetics on BSP uptake. This study showed substrate-dependent inhibition of OATP1B1 and demonstrated that E₂G was the most sensitive in vitro OATP1B1 probe substrate among three substrates tested. This will give us an insight into the assessment of clinically relevant OATP1B1-mediated DDI in vitro with minimum potential of false-negative prediction.

Usefulness of early morning urine <em>estrone</em>-<em>3</em>-<em>glucuronide</em> assay in the monitoring ovarian secretory function in precocious puberty.

To evaluate the usefulness of the urinary estrone-3-glucuronide (EI-3-G) in the monitoring of the ovarian function in girls, we studied 11 girls with idiopathic central precocious puberty (ICPP) treated with LHRH analogs (LHRHa) for 2-5 years. Plasma LH, FSH, 17-beta-Estradiol (E2) levels, early morning urine (EMU) E1-3-G concentrations, were assessed before and 3, 6, 12 months after the onset of treatment. As expected, mean basal plasma LH, FSH and E2 concentrations, as well as mean basal EMU E1-3-G levels were significantly (p < 0.01) higher in patients studied than in normal, age matched, prepubertal controls. Three out of the 11 sexually advanced girls showed undetectable (< 15 pg/ml) basal plasma E2 values. On the contrary, in each patient studied, individual basal E1-3-G levels were higher than in normal age-matched prepubertal girls. LHRHa treatment significantly suppressed both basal and peak stimulated plasma gonadotropins, plasma E2 and EMU E1-3-G. However, while serum E2 levels were below the assay detection limit, not allowing to assess the degree of gonadal suppression, E1-3-G urinary concentrations were detectable in each subject treated, in the range of the normal prepubertal values. EMU E1-3-G determination seems to be a very sensitive and reliable approach to the monitoring of the effectiveness of LHRHa treatment in sexually advanced girls, allowing to detect very low estrogen concentrations and to achieve the desired ovarian suppression.

<em>Estrone</em> <em>3</em>-<em>glucuronide</em> chemiluminescence immunoassay (LIA) and 17beta estradiol radioimmunoassay (RIA) in the monitoring of superovulation for in vitro fertilization (IVF): correlation with follicular parameters and oocyte maturity.

  • Many works in the literature of the last years had reported that urinary approach to superovulation study is a suitable method to evaluate ovarian response to pharmacological stimulation. Before applying urinary determination of hormonal levels with a chemiluminescence immuno assay (LIA) method in early morning urine (EMU) samples, we had studied the correlation of RIA-LIA procedures with reference to follicular volumes at hCG day and to recovered oocyte maturity; in fact follicular growth and oocyte morphological features are the main parameters to evaluate a successful induced cycle. In our department the IVF cycles are daily monitored with RIA seric E2 and LIA E1-3G determination, besides ultrasound examination of follicular growth.
  • We have studied E2 and E1-3G levels on the hCG administration day and their correlation with follicular areas and volumes; moreover, we have evaluated hormonal values on oocyte pick-up day with reference to recovered oocyte number and maturity. We have assumed as good timing for oocyte pick-up when more than 50% of recovered oocytes were of good quality (maturity score 4).
  • We have observed that the highest pre ovulatory E1-3G value is consistent with the best timing for oocyte pick-up; it’s possible to obtain a conversion coefficient follicular volumes and urinary E1-3G excretion. We have not found significant differences between plasmatic and urinary estrogenic parameters. It is important to remember the advantages connected by a not isotopic and not invasive method. The absence of discomfort for the patients may be a decisive factor to choose the monitoring method and LIA procedure may represent a valid alternative to RIA.

Estrone-3-Glucuronide (E1G) Standard, 125UL

C124-125UL Arbor Assays 125UL 147.6 EUR

Estrone-3-Glucuronide (E1G) Standard, 625UL

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DetectX® Estrone-3-Glucuronide (E1G) Antibody, 13ML

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DetectX® Estrone-3-Glucuronide (E1G) Antibody, 3ML

C122-3ML Arbor Assays 3ML 284.4 EUR

DetectX® Estrone-3-Glucuronide (E1G) Conjugate, 13ML

C123-13ML Arbor Assays 13ML 902.4 EUR

DetectX® Estrone-3-Glucuronide (E1G) Conjugate, 3ML

C123-3ML Arbor Assays 3ML 284.4 EUR

Estrone-3-Glucuronide (E1G) EIA Kit (One Plate)

K036-H1 Arbor Assays 1x96 well plate 392.4 EUR

Estrone-3-Glucuronide (E1G) EIA Kit (Five Plate)

K036-H5 Arbor Assays 5x96 well plate 1305.6 EUR

Human Estrone-3-Glucuronide (E1G)Enzyme Immunoassay ELISA Kit

QY-E05423 Qayee Biotechnology 96T 433.2 EUR

Kaempferol 3-glucuronide

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Estrone(Estrone) ELISA Kit

EU3107 FN Test 96T 628.92 EUR


A8426-5.1 ApexBio 10 mM (in 1mL DMSO) 135.6 EUR


A8426-50 ApexBio 50 mg 157.2 EUR


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Determination of the time of ovulation in chimpanzees by measurement of LH, <em>estrone</em> sulfate, and pregnanediol <em>3</em> alpha-<em>glucuronide</em> in urine: comparison with serum hormone patterns.

The concentrations of LH, total estrogens, and pregnanediol 3 alpha-glucuronide (PdG) were determined by specific radioimmunoassays on daily overnight urine samples obtained in 13 menstrual cycles of six adult female chimpanzees during the periods of increasing, maximal, and decreasing tumescence of the perineal sex skin. The peaks of estrogens and LH and the rise in PdG in urine accurately reflected the peaks of estradiol-17 beta and LH and the subsequent rise in progesterone in the serum of the same animals during the same menstrual cycles, and can be used to predict and verify the occurrence of ovulation, thus avoiding the repeated tranquilizations necessary to obtain daily blood samples.

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