Radioimmunoassay of estriol-16-glucuronide using tritiated and radioiodinated radioligands: direct radioimmunoassay of urinary estriol-16-glucuronide during the menstrual cycle

Sensitive determination of estriol-16-glucuronide using surface plasmon resonance sensing

For the quantitative evaluation of low levels of an estriol metabolite of estriol (estriol-16-glucuronide (E3-16G)) in liquid media, we developed a simple and highly sensitive immunoassay using a surface plasmon resonance (SPR) biosensor which did not require any time-consuming sample pretreatment steps. E3-16G was conjugated to ovalbumin (OVA) through an oligoethylene glycol (OEG) linker to form protein conjugates (E3-16G-OEG-OVA), which were then immobilized on a carboxymethyl dextran-coated sensor chip via amine coupling to develop inhibition immunoassays. A limit of detection (LOD) of 76 pg/mL was achieved using a rabbit anti-sheep primary antibody as a binding agent. The detection limit was further improved by using synthesized gold colloids (15 nm) as high mass labels conjugated to the primary antibody. In this Au nanoparticle-enhanced assay, the concentration of E3-16G in aqueous samples could be determined in 7.5 min at a level as low as 14 pg/mL. In addition, the high stability of the E3-16G-OEG-OVA surface gave no obvious drop in antibody-binding capability after more than 1000 binding/regeneration cycles which significantly lowered the research cost.

Measurement of urinary estriol glucuronides during the menstrual cycle by high-performance liquid chromatography

A simple high-performance liquid chromatographic (HPLC) method for measuring estriol-3-glucuronide (E3-3-G) and estriol-16-glucuronide (E3-16-G) in the urine of non-pregnant women is described. Estriol conjugates were extracted from 4 ml of urine with a small cartridge of graphitized carbon black (Carbopack B). After washing, E3-3-G and E3-16-G were desorbed separately by a two-step elution system. After solvent removal, the two glucuronides were quantified by isocratic ion-suppression HPLC with fluorimetric detection. The analytical recovery of the two estriol metabolites was about 95%. The detection limit of the method was 0.6 ng/ml for both analytes in urine, which is well below the concentrations of clinical interest, and the method is not susceptible to substantial interferences. Data relative to urinary levels of E3-3-G and E3-16-G measured by this method on a daily basis in early morning samples from nine women during their menstrual cycles were compared with those reported in the literature and obtained by radioimmunoassay techniques. Moreover, the potential use of defined changes in the concentrations of the two conjugates for predicting the fertile period of women was assessed.

Ovulation prediction: changes in the concentrations of urinary estrone-3-glucuronide, estradiol-17 beta-glucuronide and estriol-16 alpha-glucuronide during conceptional cycles

The concentrations of estrone-3-glucuronide (E1-3-G), estradiol-17 beta-glucuronide (E2-17 beta-G), estriol-16 alpha-glucuronide (E3-16 alpha-G) and LH/hCG have been measured in daily samples of early morning urine from six women who conceived during the period study. The specimens were collected from the second day of menstruation until the values for hCG were greater than 200 U/l. The aim of the study was to assess which of the metabolites should be measured preferentially to predict ovulation by 72 h and hence identify the probable start of the fertile period. The peak of LH was used as a reference point for ovulation and defined as Day 0. A defined rise (50% increase over the mean of three preceding values) in the concentration of each steroid metabolite occurred on the following days (mean and range): E1-3-G Day LH-4.7 (-3 to -6), E2-17 beta-G Day LH-3.7 (-3 to -6) and E3-16 alpha-G Day LH-4.5 (-3 to -6). The concentration (nmol/l; mean and range) of each metabolite on the day of the rise was: E1-3-G (106; 78-137), E2-17 beta-G (19; 5 to 27) and E3-16 alpha-G (28; 18-40). It is concluded that the measurement of each estrogen glucuronide provides similar information and quantitatively E1-3-G is the most important.