Development of a monoclonal antibody to 6 beta-hydroxycortisol and its application in an enzyme-linked immunosorbent assay (ELISA) for 6 beta-hydroxycortisol in urine

Detection of pregnancy and fertility status in big cats using an enzyme immunoassay based on 5α-pregnan-3α-ol-20-one

Development of non-invasive steroid hormone assays using fecal samples is crucial for detection of pregnancy and monitoring of fertility status in big cats and thus facilitates conservation and management of wild animals. Due to changes in metabolism and excretory pattern, animals excrete different steroid metabolites in feces and urine. The present study is an attempt to develop a common enzyme immunoassay for 5α-pregnan-3α-ol-20-one one of the predominant progestogen metabolites in the feces samples of big cats. The developed ELISA showed a high sensitivity and low cross reactivity to other hormones compared to commercially available RIA kits based on progesterone antibody. It could be used in a wide range of animals for monitoring fertility status and pregnancy detection by measuring fecal steroid metabolites.

Development and validation of a simple and direct ELISA method for the determination of conjugated (glucuronide) and non-conjugated testosterone excretion in urine

BACKGROUND

Several methods are now available to estimate urinary testosterone levels that can only be performed in established big laboratories using GC/MS techniques. In clinical practice or for research projects, an inexpensive method that does not require skilled technicians would be useful. A simple, rapid and accurate ELISA method has been developed and applied in our laboratory to measure urinary non-conjugated and total testosterone.

METHODS

High affinity anti-testosterone antibody and HRP-Donkey anti-sheep IgG (Horse Radish Peroxidase) as enzyme tracer were used to develop the ELISA method. The assay was evaluated for specificity, sensitivity, parallelism, accuracy and imprecision by the established methods on samples obtained from healthy volunteers. The results from the direct ELISA were compared to those after enzyme hydrolysis plus solvent extraction and HPLC or commercial kits.

RESULTS

A satisfactory standard curve for the direct testosterone ELISA has been developed with good sensitivity. Cross-reactivity values of anti-testosterone antibody with major interfering steroids were minimal except for testosterone-3-glucuronide (58.8%). The validity of urinary testosterone assay was confirmed by the good correlation between the results obtained by the direct ELISA and those after enzyme hydrolysis and solvent extraction (Y = 0.987X + 0.398, R2 = 0.97). Accuracy studies, parallelism and imprecision data were determined and all found to be satisfactory. Urinary testosterone excretion values obtained by our direct ELISA from healthy volunteers were generally in agreement with those published by other workers. Male urinary total testosterone excretion (non-conjugated and testosterone glucuronide) ranged from 177.9 to 865.3 nmol/day, which was about 3-6 times more than the range for women urinary testosterone excretion (34.5-308.8 nmol/day).

CONCLUSION

A direct, reliable, easy to perform, sensitive and highly specific ELISA type assay for the measurement of total testosterone in urine samples (conjugated and non-conjugated) has been developed. The novel features of the assay are that it does not require an initial extraction step or involve time consuming procedures such as chromatography. A simple method has also been developed to measure non-conjugated urinary testosterone excretion after solvent extraction alone.

Simple and sensitive high-performance liquid chromatography method for simultaneous determination of urinary free cortisol and 6beta-hydroxycortisol in routine practice. For CYP 3A4 activity evaluation in basal conditions and after grapefruit juice intake

Cytochrome p450 3A4 activity displays a wide variability. The urinary 6beta-hydroxycortisol to cortisol ratio, as a non-invasive assay, can be useful for its pretherapeutic characterization. We developed an HPLC-UV method preceded by liquid-liquid extraction for assessment of this ratio in clinical practice. Urine was collected on second void morning-spot sample. Percentage recoveries were high and reproducible. The 6beta-hydroxycortisol to cortisol ratio ranged from 1.6 to 9.9 in 12 Caucasian healthy volunteers. It was reduced by 30 to 70% after ingestion of white grapefruit juice, a CYP3A4 inhibitor. Our method, simple, sensitive and accurate, could be helpful for determination of CYP 3A4 activity before oral chemotherapy, or for the monitoring of the use of grapefruit juice as a pharmacological modulator.

Simultaneous determination of urinary free cortisol and 6beta-hydroxycortisol by liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometry and its application for estimating hepatic CYP3A induction

A reversed-phase high-performance liquid chromatography coupled to atmospheric pressure chemical ionization tandem mass spectrometry (HPLC-APCI-MS-MS) assay was developed to simultaneously determine monkey urinary free cortisol (C) and 6beta-hydroxycortisol (6beta-OHC) in 8 min. Urine sample (0.5 ml) containing fludrocortisone acetate (F-C) as the internal standard was extracted with ethyl acetate for 5 min with an extraction efficiency of 90% and 75% for C and 6beta-OHC, respectively. A Perkin-Elmer Sciex API 3000 triple quadruple instrument was used for mass spectrometric detection and the column eluent was directed to a heated nebulizer probe. The assay was linear over the range 0.25-10 microM for each analyte. The intra- and inter-day relative standard deviation (RSD) over the entire concentration range for both analytes was less than 10%. Accuracy determined at three concentrations (0.8, 2.0 and 8.0 microM) ranged between 95.5 and 108%. The method described herein is suitable for the rapid and efficient measurement of 6beta-OHC/C ratio in Rhesus monkey urine following administration of known hepatic CYP3A inducers and can be used to estimate potential CYP3A induction by drug candidates in the process of early drug development.